Projection screen

ABSTRACT

Provided is a projection screen that can effectively diffuse incident light coming from a wide range of angles in the transverse direction and the longitudinal direction and can provide a wide viewing angle even if the projection screen is applied to a large-sized screen. Disclosed is a projection screen including a light diffusion control plate, in which when a first direction and a second direction orthogonally intersecting each other are assumed to be on the surface of the light diffusion control plate, and when the incident angle of the light incident to the light diffusion control plate is defined such that an angle parallel to the normal line to the surface of the light diffusion control plate is defined as 0°, in a case in which the luminance of diffused light obtainable when light is incident at an incident angle of 0° is designated as L 0 ; the luminance of diffused light obtainable when light is incident at a predetermined incident angle along the first direction is designated as L 1 ; and the luminance of diffused light obtainable when light is incident at a predetermined incident angle along the second direction is designated as L 2 , there exist a first direction and a second direction, in which L 0 , L 1 , and L 2  always satisfy the following relational expressions (1) and (2):
 
 L   1 ≥0.25× L   0   (1)
 
 L   2 ≥0.25× L   0   (2).

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a projection screen.

More particularly, the invention relates to a projection screen, withwhich incident light coming from a wide range of angles in thetransverse direction and the vertical direction can be effectivelydiffused, and a wide viewing angle can be obtained even in a case inwhich the projection screen is applied to large-sized screens.

2. Description of the Related Art

A rear projection display is also referred to as rear surface projectiontype display apparatus and is a display mode in which an image projectedfrom the back surface side of a screen with a projector is viewed fromthe front surface side of the screen.

Regarding a transmission type projection screen used in such a rearprojection display (hereinafter, may be referred to as “rear projectionscreen”), a projection screen produced by combining a Fresnel lens and alenticular lens is known.

However, in regard to such conventional rear projection screens,generally, there has been a problem that the screen image is not brightenough, and a moiré pattern attributed to the pitch is likely to begenerated in the screen image.

In this regard, a rear projection screen which utilizes a lightdiffusion control film has been suggested as a rear projection screen ofa new type that does not use a conventional Fresnel lens or aconventional lenticular lens (see, for example, JP 2005-316354 A(Claims)).

Here, a light diffusion control film refers to a film in which thediffusion state of exiting light changes depending on the angle ofincidence of the incident light.

Specifically, a light diffusion control film refers to a film in which acertain light diffusion state is shown in a predetermined range ofincident angle (hereinafter, may be referred to as “light diffusionincident angle domain”), and in an incident angle range that deviatesfrom the light diffusion incident angle domain, the incident light isdirectly transmitted or shows a light diffusion state that is differentfrom the light diffusion state shown in the light diffusion incidentangle domain.

Regarding such a light diffusion control film, several types are known;however, for example, a light diffusion control film having a louverstructure, in which a plurality of plate-shaped regions having differentrefractive indices are alternately arranged in any one direction alongthe film plane, is widely used.

That is, JP 2005-316354 A discloses a rear projection screen formed bylaminating a plurality of sheets of a light control film (lightdiffusion control film), in which the haze value is angle-dependent, andthe light diffusion angle range that presents a haze value of 60% orhigher when light is incident at an angle of 0° to 180° with respect tothe surface is 30° or greater.

According to JP 2005-316354 A, as illustrated in FIGS. 44A and 44B, alight diffusion control film is produced by irradiating a photocurableresin composition film 320 that is transported by a conveyor 310, withlight from a rod-shaped light source lamp 315 through slits. Thus, it isunderstood that the light diffusion control film thus obtainable is alight diffusion control film of the type having the above-mentionedlouver structure.

Furthermore, regarding the lamination mode for the light diffusioncontrol film, as illustrated in FIG. 45, a mode in which sheets of thelight diffusion control film are laminated such that the directions ofthe light scattering angle ranges will almost orthogonally intersecteach other, and the like have been disclosed.

SUMMARY OF THE INVENTION

However, the rear projection screen described in JP 2005-316354 A isconfigured such that the light diffusion control film used thereinmerely has a louver structure with a single angle of inclination as theinternal structure. Therefore, there is a problem that when 3 to 4sheets of the light diffusion control film are simply laminated, it isdifficult to diffuse incident light coming from a wide anglesufficiently.

Particularly, rear projection screens are expected to be applied toapplications that have large-sized screens and are viewed at the sametime by many viewers, for example, digital signage.

However, in a case in which incident light coming from a wide angle maynot be sufficiently diffused, the viewing angle is inevitably narrowed,and it will be difficult to apply the rear projection screens to therelevant applications.

In this regard, in the case of the rear projection screen described inJP 2005-316354 A, since the performance of each sheet of the lightdiffusion control film is insufficient, there is a problem that eventhough those sheets are laminated such that the directions of the lightscattering angle ranges would almost orthogonally intersect each otheras illustrated in FIG. 45, such requirements may not be satisfied.

When the number of laminated sheets of a light diffusion control film isfurther increased in order to effectively diffuse incident light comingfrom a wide angle, there is a problem that as the thickness of thelaminate thus obtainable increases, the degree of sharpness of theimages thus obtainable is decreased, and blurred images are likely to beproduced.

Thus, the inventors of the present invention conducted a thoroughinvestigation in view of such circumstances as described above, and theinventors found that when a light diffusion control plate formed toinclude a light diffusion control film having a predetermined internalstructure within the film is used, and also, the light diffusioncharacteristics in the case of changing the angle of incidence ofincident light with respect to two orthogonally intersecting directionsalong the surface of such a light diffusion control plate are specifiedin a predetermined range, incident light coming from a wide range ofangles in the transverse direction and the vertical direction can beefficiently diffused.

It was found that when such a predetermined light diffusion controlplate is used, a rear projection screen having a wide viewing angle evenin a case in which the light diffusion control plate is applied to alarge-sized screen, can be obtained. It was also found that when such alight diffusion control plate is used, a front projection screenpresenting similar effects is also obtained. Thus, the inventorscompleted the present invention.

That is, an object of the invention is to provide a projection screen,with which incident light coming from a wide range of angles in thetransverse direction and the vertical direction can be effectivelydiffused, and a wide viewing angle can be obtained even when theprojection screen is applied to a large-sized screen.

According to an aspect of the invention, there is provided a projectionscreen comprising a light diffusion control plate, the light diffusioncontrol plate including a light diffusion control film having internalstructures each including a plurality of regions having a relativelyhigh refractive index in a region having a relatively low refractiveindex in the interior of the film, in which when a first direction and asecond direction orthogonally intersecting each other are assumed to beon the surface of the light diffusion control plate, and when theincident angle of the light incident to the light diffusion controlplate is defined such that an angle parallel to the normal line to thesurface of the light diffusion control plate is defined as 0°, in a casein which the luminance of diffused light obtainable when light isincident on the intersection point of the orthogonally intersectingfirst direction and second direction at an incident angle of 0° isdesignated as L₀ (candela per square meter (cd/m²)); the luminance ofdiffused light obtainable when light is incident on the intersectionpoint of the orthogonally intersecting first direction and seconddirection at an incident angle varying in the range of −30° to 30° alongthe first direction is designated as L₁ (cd/m²); and the luminance ofdiffused light obtainable when light is incident on the intersectionpoint of the orthogonally intersecting first direction and seconddirection at an incident angle varying in the range of 0° to 30° alongthe second direction is designated as L₂ (cd/m²), there exist the firstdirection and the second direction, in which L₀, L₁, and L₂ alwayssatisfy the following relational expressions (1) and (2):L ₁≥0.25×L ₀  (1)L ₂≥0.25×L ₀  (2).Thus, the problems described above can be addressed.

That is, the projection screen of the invention uses a light diffusioncontrol plate formed to include a light diffusion control film having apredetermined internal structure in the film, and also the lightdiffusion characteristics obtainable in the case of varying the incidentangle of incident light in two orthogonally intersecting directionsalong the surface of such a light diffusion control plate are defined tobe in a predetermined range.

Therefore, incident light coming from a wide range of angles in thetransverse direction and the vertical direction can be effectivelydiffused, and even in a case in which the projection screen is appliedto a large-sized screen, a wide viewing angle can be obtained.

Meanwhile, the term “projection screen” means a screen on which an imageis displayed, as light from a projector is illuminated against aprojection display.

Furthermore, L₀, L₁, L₂, and L₃(−30°) that will be described below meanluminance values measured in the front direction of the light diffusioncontrol plate.

Upon configuring the projection screen of the invention, in a case inwhich the luminance of diffused light obtainable when light is incidenton the intersection point of the orthogonally intersecting firstdirection and second direction at an incident angle of −30° along thesecond direction is designated as L₃(−30°) (cd/m³), it is preferablethat L₃(−30°) satisfies the following relational expression (3):L ₃(−30°)<0.7×L ₀  (3)

Even in a case in which the projection screen is configured as such,incident light coming from a wide range of angles in the transversedirection and the vertical direction can be effectively diffused,without limiting the usage of the projection screen by any means.

Upon configuring the projection screen of the invention, in regard tothe light diffusion control plate, it is preferable that thetransmission gain at the time of setting the incident angle to 0° isadjusted to a value of 0.8 or higher.

When the projection screen is configured as such, incident light comingfrom a wide range of angles in the transverse direction and the verticaldirection can be effectively diffused while effectively maintaining thebrightness of images displayed.

Upon configuring the projection screen of the invention, it ispreferable that the light diffusion control plate is formed bylaminating a plurality of sheets of a light diffusion control film, andthe number of laminated sheets of the light diffusion control film isadjusted to 4 or less.

When the projection screen is configured as such, the occurrence ofblurred images is suppressed, and incident light coming from a widerange of angles in the transverse direction and the vertical directioncan be effectively diffused without excessively lowering the productionefficiency.

Upon configuring the projection screen of the invention, it ispreferable that the light diffusion control film includes a lightdiffusion control film having a single light diffusion layer that has afirst internal structure and a second internal structure, the structureseach including a plurality of regions having a relatively highrefractive index in a region having a relatively low refractive index inthe interior of the film, sequentially from the lower part along thefilm thickness direction.

When the projection screen is configured as such, incident light comingfrom a wide range of angles in the transverse direction and the verticaldirection can be effectively diffused while reducing the number oflaminated sheets of the light diffusion control film.

Meanwhile, the term “single layer” means that a plurality of sheets of alight diffusion control film is not laminated.

Furthermore, upon configuring the projection screen of the invention, itis preferable that the projection screen has an overlapping internalstructure in which the position of the upper end portion of the firstinternal structure and the position of the lower end portion of thesecond internal structure overlap each other in the film thicknessdirection.

When the projection screen is configured as such, incident light beingdirectly transmitted and thereby straight-traveling transmitted lightbeing incorporated into the diffused light can be effectivelysuppressed, and uniformity of the intensity of diffused light can beenhanced, as compared to the case in which an internalstructure-unformed area exists between the respective internalstructures.

Upon configuring the projection screen of the invention, it ispreferable that the thickness of the overlapping internal structure isadjusted to a value within the range of 1 to 40 μm.

When the projection screen is configured as such, since incident lightis directly transmitted, incorporation of straight-traveling transmittedlight into diffused light can be more effectively suppressed, anduniformity of the intensity of diffused light can be enhanced.

Upon configuring the projection screen of the invention, it ispreferable that the incident angle θ1 of the region having a relativelyhigh refractive index in the first internal structure with respect tothe normal line to the film plane is adjusted to a value within therange of 0° to 80°, and the incident angle θ2 of the region having arelatively high refractive index in the second internal structure withrespect to the normal line to the film plane is adjusted to a valuewithin the range of 0° to 45°.

When the projection screen is configured as such, incident light comingfrom a wide angle can be diffused more effectively.

Furthermore, upon configuring the projection screen of the invention, itis preferable that the first internal structure is a columnar structureobtained by arranging a plurality of pillar-shaped objects having arelatively high refractive index to stand close together in the filmthickness direction in a region having a relatively low refractiveindex, or a louver structure obtained by alternately arranging aplurality of plate-shaped regions having different refractive indices inany one direction along the film plane.

When the projection screen is configured as such, incident light comingfrom a wide angle can be diffused more effectively.

Furthermore, upon configuring the projection screen of the invention, itis preferable that the second internal structure is a columnar structureobtained by arranging a plurality of pillar-shaped objects having arelatively high refractive index to stand close together in the filmthickness direction in a region having a relatively low refractiveindex, or a louver structure obtained by alternately arranging aplurality of plate-shaped regions having different refractive indices inany one direction along the film plane.

When the projection screen is configured as such, incident light comingfrom a wide range of angles can be diffused more effectively.

Furthermore, upon configuring the projection screen of the invention isconfigured, it is preferable that the thickness of the light diffusioncontrol plate is adjusted to a value within the range of 186 to 3,600μm.

When the projection screen is configured as such, incident light comingfrom a projector can be diffused more uniformly without depending on theangle of incidence, while suppressing the occurrence of blurred images.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram provided to explain the configuration and the lightdiffusion characteristics of a light diffusion control film having apredetermined internal structure according to the present invention;

FIGS. 2A and 2B are other diagrams provided to explain the configurationof the light diffusion control film having a predetermined internalstructure according to the invention;

FIG. 3 is a diagram provided to explain the light diffusioncharacteristics of the light diffusion control film having apredetermined internal structure according to the invention;

FIG. 4 is a diagram provided to explain the light diffusioncharacteristics obtainable in a case in which a plurality of sheets ofthe light diffusion control film having a predetermined internalstructure according to the invention are laminated;

FIGS. 5A and 5B are still other diagrams provided to explain theconfiguration of the light diffusion control film having a predeterminedinternal structure according to the invention;

FIGS. 6A and 6B are diagrams provided to explain the shapes of anoverlapping internal structure;

FIGS. 7A to 7C are diagrams provided to explain the method for producinga light diffusion control film having a predetermined internal structureaccording to the invention;

FIG. 8 is a diagram provided to explain the angle of irradiation ofactive energy radiation;

FIGS. 9A to 9D are diagrams provided to explain other embodiments of thelight diffusion control film having a predetermined internal structureaccording to the invention;

FIGS. 10A to 10C are diagrams provided to explain the light diffusioncharacteristics of a light diffusion control plate according to theinvention;

FIGS. 11A and 11B are other diagrams provided to explain the lightdiffusion characteristics of the light diffusion control plate accordingto the invention;

FIGS. 12A and 12B are diagrams provided to explain a schematiccross-sectional view and a photograph of a light diffusion control filmused in Example 1, the light diffusion control film having alouver-columnar structure;

FIGS. 13A and 13B are diagrams provided to explain the light diffusioncharacteristics of the light diffusion control film used in Example 1,the light diffusion control film having a louver-columnar structure;

FIGS. 14A and 14B are diagrams provided to explain a schematiccross-sectional view and a photograph of a light diffusion control filmused in Example 1, the light diffusion control film having a columnarstructure only;

FIGS. 15A and 15B are diagrams provided to explain the configuration andthe light diffusion characteristics of a rear projection screen ofExample 1;

FIG. 16 is a diagram provided to explain a method for performing imageevaluation using a projector;

FIGS. 17A to 17C are diagrams provided to shown particular imagesprojected at the time of image evaluation using a projector in Example1;

FIGS. 18A and 18B are diagrams provided to explain the configuration andthe light diffusion characteristics of a rear projection screen ofExample 2;

FIG. 19 is a diagram provided to explain a schematic cross-sectionalview of a light diffusion control film used in Example 2, the lightdiffusion control film having a bent louver-columnar structure;

FIGS. 20A and 20B are diagrams provided to explain the configuration andthe light diffusion characteristics of a rear projection screen ofExample 3;

FIGS. 21A and 21B are diagrams provided to explain the configuration andthe light diffusion characteristics of a rear projection screen ofExample 4;

FIGS. 22A and 22B are diagrams provided to explain the configuration andthe light diffusion characteristics of a rear projection screen ofExample 5;

FIGS. 23A and 23B are diagrams provided to explain the configuration andthe light diffusion characteristics of a rear projection screen ofExample 6;

FIGS. 24A and 24B are diagrams provided to explain the configuration andthe light diffusion characteristics of a rear projection screen ofExample 7;

FIGS. 25A and 25B are diagrams provided to explain a schematiccross-sectional view and a photograph of a light diffusion control filmused in Example 7, the light diffusion control film having a columnarstructure only;

FIGS. 26A and 26B are diagrams provided to explain the configuration andthe light diffusion characteristics of a rear projection screen ofExample 8;

FIGS. 27A and 27B are diagrams provided to explain a schematiccross-sectional view and a photograph of a light diffusion control filmused in Example 8, the light diffusion control film having acolumnar-columnar structure;

FIGS. 28A to 28C are diagrams provided to show the particular imagesprojected at the time of image evaluation using a projector in Example8;

FIGS. 29A and 29B are diagrams provided to explain the configuration andthe light diffusion characteristics of a rear projection screen ofExample 9;

FIGS. 30A and 30B are diagrams provided to explain a schematiccross-sectional view and a photograph of a light diffusion control filmused in Example 9, the light diffusion control film having a bentcolumnar-columnar structure;

FIGS. 31A and 31B are diagrams provided to explain the configuration andthe light diffusion characteristics of a rear projection screen ofExample 10;

FIGS. 32A and 32B are diagrams provided to explain the configuration andthe light diffusion characteristics of a rear projection screen ofExample 11;

FIGS. 33A and 33B are diagrams provided to explain the configuration andthe light diffusion characteristics of a rear projection screen ofExample 12;

FIGS. 34A and 34B are diagrams provided to explain the configuration andthe light diffusion characteristics of a rear projection screen ofExample 13;

FIGS. 35A and 35B are diagrams provided to explain the configuration andthe light diffusion characteristics of a rear projection screen ofComparative Example 1;

FIGS. 36A and 36B are diagrams provided to explain the configuration andthe light diffusion characteristics of a rear projection screen ofComparative Example 2;

FIGS. 37A to 37C are diagrams provided to show the particular imagesprojected at the time of image evaluation using a projector inComparative Example 2;

FIGS. 38A and 38B are diagrams provided to explain the configuration andthe light diffusion characteristics of a rear projection screen ofComparative Example 3;

FIGS. 39A and 39B are diagrams provided to explain a schematiccross-sectional view and a photograph of the light diffusion controlfilm used in Comparative Example 3, the light diffusion control filmhaving a louver structure only;

FIGS. 40A to 40C are diagrams provided to show the particular imagesprojected at the time of image evaluation using a projector inComparative Example 3;

FIGS. 41A and 41B are diagrams provided to explain the configuration andthe light diffusion characteristics of a rear projection screen ofComparative Example 4;

FIGS. 42A and 42B are diagrams provided to explain a schematiccross-sectional view and a photograph of the light diffusion controlfilm used in Comparative Example 4, the light diffusion control filmhaving a louver structure only;

FIGS. 43A to 43C are diagrams provided to show the particular imagesprojected at the time of image evaluation using a projector inComparative Example 4;

FIGS. 44A and 44B are diagrams provided to explain a conventional rearprojection screen; and

FIG. 45 is another diagram provided to explain a conventional rearprojection screen.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to embodiments of the invention, there is provided aprojection screen comprising a light diffusion control plate, the lightdiffusion control plate including a light diffusion control film havingan internal structure including a plurality of regions having arelatively high refractive index in a region having a relatively lowrefractive index in the interior of the film, in which when a firstdirection and a second direction orthogonally intersecting each otherare assumed to be on the surface of the light diffusion control plate,and when the incident angle of the light incident to the light diffusioncontrol plate is defined such that an angle parallel to the normal lineto the surface of the light diffusion control plate is defined as 0°, ina case in which the luminance of diffused light obtainable when light isincident on the intersection point of the orthogonally intersectingfirst direction and second direction at an incident angle of 0° isdesignated as L₀ (cd/m²); the luminance of diffused light obtainablewhen light is incident on the intersection point of the orthogonallyintersecting first direction and second direction at an incident anglevarying in the range of −30° to 30° along the first direction isdesignated as L₁ (cd/m²); and the luminance of diffused light obtainablewhen light is incident on the intersection point of the orthogonallyintersecting first direction and second direction at an incident anglevarying in the range of 0° to 30° along the second direction isdesignated as L₂ (cd/m²), there exist the first direction and the seconddirection, in which L₀, L₁, and L₂ always satisfy the followingrelational expressions (1) and (2):L ₁≥0.25×L ₀  (1)L ₂≥0.25×L ₀  (2)

In the following description, embodiments of the invention will bespecifically described with reference to the drawings as appropriate.

1. Light Diffusion Control Film

The light diffusion control plate used in the projection screen of theinvention comprises a light diffusion control film having an internalstructure including a plurality of regions having a relatively highrefractive index in a region having a relatively low refractive index inthe interior of the film.

The reason for this is that when a combination of a Fresnel lens and alenticular lens, which are conventionally well known, is used as a lightdiffusion control plate, a problem that the screen image becomes dim ora moiré pattern induced by the pitch is generated on the screen image,may easily occur.

In this regard, the light diffusion control film having a predeterminedinternal structure according to the invention has characteristics bywhich distinction between the light diffusion incident angle domain andother incident angle domains can be clearly made due to such apredetermined internal structure (hereinafter, may be referred to as“incident angle-dependency”).

Furthermore, the light diffusion control film according to the inventionhas characteristics by which, even in a case in which the incident angleof incident light changes within the light diffusion incident angledomain, the direction, range of diffusion, and intensity of the diffusedlight are maintained constant (hereinafter, may be referred to as“non-incident angle-dependency”).

Thereby, when the light diffusion incident angle domain is regulatedbased on the mode of lamination of the light diffusion control film,incident light coming from a wide range of angles in the transversedirection and the vertical direction can be effectively diffused.

Furthermore, due to the non-incident angle-dependency, incident lightcoming from a wide range of angles in the transverse direction and thevertical direction can be stably diffused at a constant luminance in adesired direction including the front direction of the projectionscreen, and thus a wide viewing angle can be obtained.

Therefore, by using the light diffusion control film having apredetermined internal structure, a problem that the screen imagebecomes dim or a moiré pattern induced by the pitch is generated in thescreen image as in the case of using a Fresnel lens and a lenticularlens can be addressed effectively, and a projection screen havingsuperior light diffusion characteristics can be obtained.

Regarding such a light diffusion control film having a predeterminedinternal structure, various embodiments are available; however, ageneral example thereof may be, as illustrated in FIG. 1, a lightdiffusion control film 10 having, in the interior of the film 10, acolumnar structure s obtained by arranging a plurality of pillar-shapedobjects 14 having a relatively high refractive index to stand closetogether in the film thickness direction in a region 11 having arelatively low refractive index.

In the light diffusion control film having such a predetermined internalstructure, as illustrated in FIG. 1, regarding incident light B that hasentered through the light diffusion incident angle domain, the lightthat has entered the region having a relatively high refractive index,such as the pillar-shaped objects 14, is diffused as the light escapesthe film while being repeatedly reflected at the interface between theregion having a relatively high refractive index and the region 11having a relatively low refractive index.

On the other hand, incident light (A or C) that has entered through aregion outside the light diffusion incident angle domain undergoescrescent-shaped light diffusion with an extremely narrowed diffusionwidth of the diffused light, or is directly transmitted out of the lightdiffusion control film.

FIG. 1 is a perspective view illustrating the entirety of the lightdiffusion control film 10 having only a columnar structure s in theinterior of the film, and the light diffusion characteristics of thefilm.

It is also preferable that the light diffusion control film includes alight diffusion control film having a single light diffusion layerhaving, in the interior of the film, a first internal structure and asecond internal structure each having a plurality of regions having arelatively high refractive index in a region having a relatively lowrefractive index, as the light diffusion control film having apredetermined internal structure.

The reason for this is that when a light diffusion control film having afirst internal structure and a second internal structure is used,incident light coming from a wide range of angles in the transversedirection and the vertical direction can be effectively diffused whilereducing the number of laminated sheets of the light diffusion controlfilm.

That is, it is because when the range of the light diffusioncharacteristics originating from the first internal structure and therange of the light diffusion characteristics originating from the secondinternal structure are shifted while making some portions of the rangesto overlap each other, the comprehensive range of the light diffusioncharacteristics of the light diffusion control film can be extendedeffectively, and moreover, the range of the light diffusioncharacteristics of the light diffusion control plate can also beextended effectively.

The term “range of the light diffusion characteristics” means the rangeof the angle of incidence that shows incident angle dependency, and therange of spread of the diffused light.

It is preferable that the first internal structure is a columnarstructure obtainable by arranging a plurality of pillar-shaped objectshaving a relatively high refractive index to stand close together in thefilm thickness direction in a region having a relatively low refractiveindex, or a louver structure obtainable by alternately arranging aplurality of plate-shaped regions having different refractive indices inany one direction along the film plane.

It is preferable that the second internal structure is also a columnarstructure obtainable by arranging a plurality of pillar-shaped objectshaving a relatively high refractive index to stand close together in thefilm thickness direction in a region having a relatively low refractiveindex, or a louver structure obtainable by alternately arranging aplurality of plate-shaped regions having different refractive indices inany one direction along the film plane.

The reason for this is that when the light diffusion control film isconfigured as such, the range of the light diffusion characteristics canbe extended more effectively.

Examples of such a light diffusion control film include, as illustratedin FIG. 2A, a light diffusion control film 10′ in which the firstinternal structure 20 is a louver structure 20 t, and the secondinternal structure 30 is a columnar structure 30 s.

(1) Basic Configuration

The light diffusion control film according to the invention can adoptinternal structures of various shapes as will be disclosed in theExamples; however, in the present specification, the light diffusioncontrol film will be specifically explained by taking the lightdiffusion control film 10′ illustrated in FIG. 2A as an example.

First, the basic configuration of the light diffusion control film 10′having predetermined internal structures (20 t and 30 s) will bespecifically described using FIGS. 2A and 2B.

Here, FIG. 2A shows a perspective view illustrating the entirety of thelight diffusion control film 10′ having predetermined internalstructures (20 t and 30 s), and FIG. 2B shows a cross-sectional view ofthe light diffusion control film 10′ having predetermined internalstructures (20 t and 30 s) of FIG. 2A.

As illustrated in such FIGS. 2A and 2B, the light diffusion control film10′ having predetermined internal structures (20 t and 30 s) is a lightdiffusion control film 10′ having a single light diffusion layer 50having a first internal structure 20 for anisotropically diffusingincident light and a second internal structure 30 for isotropicallydiffusing incident light sequentially from the lower part long the filmthickness direction.

More specifically, the first internal structure 20 is a louver structure20 t obtainable by alternately arranging a plurality of plate-shapedregions having different refractive indices (plate-shaped regions 11having relatively low refractive index and plate-shaped regions 12having a relatively high refractive index) in any one direction alongthe film plane, and the second internal structure 30 is a columnarstructure 30 s obtainable by arranging a plurality of pillar-shapedobjects 14 having a relatively high refractive index to stand closetogether in the film thickness direction in a region 11 having arelatively low refractive index.

The louver structure 20 t as the first internal structure 20 may beconstrued as an internal structure formed by arranging a plurality ofthe plate-shaped regions 12 having a relatively high refractive indexparallel to one another in the film thickness direction in the region 11having a relatively low refractive index.

(2) Light Diffusion Characteristics

Next, the light diffusion characteristics of the light diffusion controlfilm 10′ having predetermined internal structures (20 t and 30 s) willbe specifically described using FIG. 3.

Here, FIG. 3 shows, in regard to the light diffusion control film 10′having a louver structure 20 t as the first internal structure 20 and acolumnar structure 30 s as the second internal structure 30 according tothe invention, the light diffusion characteristics in the case ofcausing light to enter through a lateral side of the columnar structure30 s are illustrated separately in a stage in which the incident lightis diffused by the columnar structure 30 s only, and in a stage in whichthe light diffused by the columnar structure 30 s is further diffused bythe louver structure 20 t.

As illustrated in such FIG. 3, since the columnar structure 30 s as thesecond internal structure 30 has a property of isotropically diffusingincident light, the diffused light obtained in the stage of diffusinglight by means of the columnar structure 30 s only is projected into acircular shaped on the paper plane that is parallel to the lightdiffusion control film.

In FIG. 3, the unit for the axis of ordinate and the axis of abscissa inthe coordinate system shown in the paper plane that is parallel to thelight diffusion control film is the angle (°), and the coordinates meanthe exit angle of diffused light in various directions.

Meanwhile, since the louver structure 20 t as the first internalstructure 20 has a property of anisotropically diffusing incident light,the diffused light that has been diffused by means of the first internalstructure 20 only is projected into a straight line shape on the paperplane that is parallel to the light diffusion control film (not shown inthe diagram).

Therefore, as illustrated in FIG. 3, the diffused light obtained in thestage in which the light that has been diffused by means of the columnarstructure 30 s is further diffused by means of the louver structure 20t, that is, the diffused light that has been diffused by means of thelight diffusion control film 10′, is projected into a bullet shapefacing right to the paper plane, on the paper plane that is parallel tothe light diffusion control film.

More specifically, since the upper edges of the plate-shaped regions (11and 12) that constitute the louver structure 20 t are inclined to theright side of the paper plane, the right half in the paper plane of thecircular-shaped diffused light produced by the columnar structure 30 sis such that the direction of progress thereof is different from theangle of inclination of the plate-shaped regions (11 and 12), by apredetermined angle or greater.

Therefore, the right half in the paper plane of the circular-shapeddiffused light produced by the columnar structure 30 s is directlytransmitted through the louver structure 20 t.

On the other hand, the left half in the paper plane of thecircular-shaped diffused light produced by the columnar structure 30 sis such that the direction of progress thereof approximates the angle ofinclination of the plate-shaped regions (11 and 12) by a predeterminedangle or greater. Therefore, the left half in the paper plane isanisotropically diffused, by means of the louver structure 20 t, into ashape that is extended in the horizontal direction in the paper plane(hereinafter, such a direction of anisotropic diffusion may be expressedas “direction of anisotropic diffusion (ID): ⇔”).

According to the present specification, the symbol “⇔” means theleftward and rightward directions in the paper plane, the symbol “←”means the leftward direction in the paper plane, the symbol “→” meansthe rightward direction in the paper plane, the symbol “●” means theforward direction in the paper plane, and the symbol “◯” means thebackward direction in the paper plane.

Furthermore, not only that, such diffused light that has beenanisotropically diffused exits in a direction deviated to the left sideof the paper plane, due to the inclination of the plate-shaped regions(11 and 12) (hereinafter, the direction of deviation in such an exitdirection may be expressed as “direction of exit (PD): ←”).

Based on the above-described mechanism, as illustrated in FIG. 3, thediffused light that has been diffused by light diffusion control film10′ having predetermined internal structures (20 t and 30 s) isprojected into a bullet shape on the paper plane that is parallel to thelight diffusion control film 10′.

Even with identical light diffusion control films, if light is madeincident through opposite directions, the directions of exit (PD) are incounter directions.

Next, the light diffusion characteristics obtainable in the case oflaminating a plurality of sheets of the light diffusion control film 10′having predetermined internal structures (20 t and 30 s) will beexplained using FIG. 4.

Here, FIG. 4 shows the light diffusion characteristics obtainable in acase in which light is caused to enter a laminate formed by laminating alight diffusion control film 10′ having the predetermined internalstructures (20 t and 30 s) illustrated in FIG. 3 (ID: ⇔, PD: ←), thesame light diffusion control film 10′ (ID: ⇔, PD: →), and the same lightdiffusion control film 10′ (ID: ●, PD: ●), through a lateral side of thecolumnar structure 30 s in the respective light diffusion control films10′.

More specifically, the light diffusion characteristics of the laminateare shown separately in a stage of diffusing light by means of thecolumnar structure 30 s and a stage of further diffusing the diffusedlight by means of the louver structure 20 t, for each of the lightdiffusion control films 10′.

First, as illustrated in (i) of FIG. 4, the columnar structure 30 s asthe second internal structure 30 in the light diffusion control film 10′of the top layer diffuses light incident from a light source into acircular shape.

Next, as illustrated in (ii) of FIG. 4, the louver structure 20 t as thefirst internal structure 20 in the light diffusion control film 10′ ofthe top layer diffuses the lower half in the paper plane of thecircular-shaped diffused light that has entered the structure, in thedownward direction from the paper plane, and the louver structure 20 tdiffuses light generally into a bullet shape facing upward in the paperplane.

Next, as illustrated in (iii) of FIG. 4, the columnar structure 30 s asthe second internal structure 30 in the light diffusion control film 10′of the middle layer diffuses the light of the portion with strongstraight-traveling properties in the light that has entered the lightdiffusion control plate and has been diffused into a bullet shape facingupward in the paper plane, that is, the light in the vicinity of thecenter of the coordinate system, into a circular shape.

The outline of the diffused light at this time is still a bullet shapefacing upward in the paper plane.

Next, as illustrated in (iv) of FIG. 4, the louver structure 20 t as thefirst internal structure 20 in the light diffusion control film 10′ ofthe middle layer diffuses the light that has entered the light diffusioncontrol plate and has been diffused into a bullet shape facing upward inthe paper plane, in the rightward direction in the paper plane, and thelouver structure 20 t diffuses light generally into a quadrilateralshape with only the upper left corner in the paper plane being rounded.

Next, as illustrated in (v) of FIG. 4, the columnar structure 30 s asthe second internal structure 30 in the light diffusion control film 10′of the lowermost layer diffuses the light of the portion with strongstraight-traveling properties in the light that has entered the lightdiffusion control plate and has been diffused into a quadrilateral shapewith only the upper left corner in the paper plane being rounded, thatis, the light in the vicinity of the center of the coordinate system,into a circular shape.

The outline of the diffused light at this time is still a quadrilateralshape with only the upper left corner in the paper plane being rounded.

Next, as illustrated in (vi) of FIG. 4, the louver structure 20 t as thefirst internal structure 20 in the light diffusion control film 10′ ofthe lowermost layer diffuses the light that has entered the lightdiffusion control plate and has been diffused into a quadrilateral shapewith only the upper left corner in the paper plane being rounded, in theleftward direction in the paper plane, and the louver structure 20 tdiffuses light generally into a horizontally long rectangular shapeoccupying the lower half of the coordinate system.

Based on the above-described mechanism, as illustrated in FIG. 4, thediffused light that has been diffused by a laminate formed by laminatinga plurality of sheets of a light diffusion control film 10′ havingpredetermined internal structures (20 t and 30 s) is projected into ahorizontally long rectangular shape in the paper plane that is parallelto the laminate, as a result of laminating sheets of the light diffusioncontrol film in a predetermined mode.

In this case, light is not diffused in the upper half of the coordinatesystem; however, for example, in the case of digital signage installedat the rooftop of a building, it is acceptable as long as the screen isvisible from the front, left, right, and lower sides of the screen, andthe occasion in which the screen is viewed from the upper side is notconceived. Therefore, there is no problem for practical use in thatregard.

In contrast, when diffusion into unnecessary directions is cut off, theluminance of the light diffused into necessary directions is increased,and therefore, the brightness of the displayed image can be effectivelyincreased.

However, if more sheets of the light diffusion control film arelaminated, it is also possible to realize diffusion in all directions.

Thus, when a light diffusion control film 10′ having predeterminedinternal structures (20 t and 30 s) is used, when sheets of the lightdiffusion control film are laminated in a predetermined mode, incidentlight can be effectively diffused as illustrated in (vi) of FIG. 4, evenif a laminate of three sheets at the minimum is used.

In FIG. 4, the case in which light is incident at an angle that isperpendicular to the surface of the laminate has been explained as anexample, for convenience. However, as will be specifically described inthe Examples, the excellent light diffusion characteristics of such alaminate are stably manifested for incident light coming from a wideangle.

Such effects are attributed particularly to the fact that the columnarstructure 30 s can efficiently diffuse incident light coming from a wideangle, and the direction of inclination of the louver structure 20 tcontrols this.

To specifically explain the light diffusion characteristics of thecolumnar structure, the columnar structure has a light diffusionincident angle domain in which crescent-shaped diffusion occurs, inaddition to the light diffusion incident angle domain in which isotropicdiffusion occurs, and thus, the columnar structure is characterized inthat the comprehensive range of the light diffusion incident angledomain is very wide (for example, see the light diffusioncharacteristics of the light diffusion control film having a columnarstructure only, as illustrated in FIG. 36).

Therefore, when the light diffusion control film 10′ havingpredetermined internal structures (20 t and 30 s) is used, incidentlight coming from a wide angle can be diffused effectively by laminating3 to 4 sheets of the film in a predetermined mode.

From this, it is understood that the light diffusion control film 10′having predetermined internal structures (20 t and 30 s) is a lightdiffusion control film suitable for producing a projection screen havinga wide viewing angle that is applicable to large-sized screens.

(3) First Internal Structure

As illustrated in FIG. 2A, the first internal structure of the lightdiffusion control film 10′ according to the invention is an internalstructure for anisotropically diffusing incident light, andspecifically, the first internal structure 20 is a louver structure 20 tformed by alternately arranging a plurality of plate-shaped regions (11and 12) having different refractive indices in any one direction alongthe film plane.

The reason for this is that when the louver structure 20 t is employedas the first internal structure 20, as illustrated in FIG. 3, the lightdiffusion characteristics thus obtainable can be imparted with adirection of anisotropic diffusion (ID) or a direction of exit (PD).

As a result, along with the effects of the columnar structure 30 s asthe second internal structure 30, when sheets of a predetermined lightdiffusion control film 10′ are laminated in a predetermined mode asillustrated in FIG. 4, excellent light diffusion characteristicssuitable for large-sized projection screens can be obtained.

(3)-1 Refractive Index

In the louver structure, it is preferable that the difference betweenthe refractive index of the plate-shaped regions having a relativelyhigh refractive index and the refractive index of the plate-shapedregions having a relatively low refractive index is adjusted to a valueof 0.01 or greater.

The reason for this is that if such a difference in the refractive indexhas a value of below 0.01, since the angle range in which totalreflection of incident light within the louver structure is narrowed,the incident angle dependency may be excessively lowered.

Therefore, it is more preferable that the lower limit of such adifference in the refractive index is adjusted to a value of 0.03 orgreater, and even more preferably to a value of 0.1 or greater.

It is more preferable if such a difference in the refractive index islarger; however, from the viewpoint of selecting a material capable offorming a louver structure, it is considered that the upper limit isabout 0.3.

(3)-2 Width

Furthermore, in regard to the louver structure 20 t illustrated in FIG.2A, it is preferable that the width of the plate-shaped regions 12having a relatively high refractive index and the width of theplate-shaped regions 11 having a relatively low refractive index arerespectively adjusted to a value within the range of 0.1 to 15 μm.

The reason for this is that if such a width has a value of below 0.1 μm,it may be difficult for the light diffusion control film to show lightdiffusion characteristics, irrespective of the angle of incidence ofincident light. On the other hand, if such a width has a value of above15 μm, the amount of light that travels straight through the louverstructure increases, and the uniformity of light diffusion may bedeteriorated.

Therefore, in regard to the louver structure, it is more preferable thatthe lower limit of such a width is adjusted to a value of 0.5 μm orgreater, and even more preferably to a value of 1 μm or greater.

Furthermore, in regard to the louver structure, it is more preferablethat the upper limit of such a width is adjusted to a value of 10 μm orless, and even more preferably to a value of 5 μm or less.

The widths of the plate-shaped regions having a relatively highrefractive index and the plate-shaped regions having a relatively lowrefractive index can be calculated by making an observation of the filmwith a digital optical microscope.

(3)-3 Thickness

Furthermore, it is preferable that the thickness (length in the filmthickness direction) of the louver structure 20 t illustrated in FIG.2A, that is, length L1 in FIG. 2B, is adjusted to a value within therange of 30 to 500 μm.

The reason for this is that if such length L1 has a value of below 30μm, the amount of incident light that travels straight through thelouver structure increases, and it may be difficult to obtain asufficient range of light diffusion characteristics. Meanwhile, it isbecause if such length L1 has a value of above 500 μm, when a louverstructure is formed by irradiating a composition for a light diffusioncontrol film with active energy radiation, the direction of progress ofphotopolymerization is diffused by the louver structure formed in thebeginning, and it may be difficult to form a desired louver structure.

Therefore, it is more preferable that the lower limit of the length L1of the louver structure is adjusted to a value of 50 μm or greater, andeven more preferably to a value of 70 μm or greater.

Furthermore, it is more preferable that the upper limit of the length L1of the louver structure is adjusted to a value of 325 μm or less, andeven more preferably to a value of 200 μm or less.

(3)-4 Angle of Inclination

In regard to the louver structure 20 t illustrated in FIG. 2A, it ispreferable that plate-shaped regions (11 and 12) having differentrefractive indices are arranged to be parallel with one another at aconstant angle of inclination with respect to the film thicknessdirection.

The reason for this is that when the angle of inclination of theplate-shaped regions having different refractive indices is madeconstant, incident angle can be reflected more stably in the louverstructure, and the incident angle dependency originating from the louverstructure can be further enhanced.

More specifically, as illustrated in FIG. 2B, it is preferable that inregard to the louver structure 20 t as the first internal structure 20,the angle of inclination θ1 of the plate-shaped regions (11 and 12)having different refractive indices with respect to the normal line tothe film plane is adjusted to a value within the range of 0° to 80°.

The reason for this is that if such an angle of inclination θ1 has avalue of above 80°, since the absolute value of the incident angle ofactive energy radiation also increases with the angle of inclination,the proportion of reflection of the active energy radiation at aninterface between air and the coating layer increases, and at the timeof forming a louver structure, there is a need to irradiate the louverstructure with active energy radiation at a higher illumination.Meanwhile, if such an angle of inclination θ1 has an excessively smallvalue, it may be difficult to impart the direction of exit (PD) to thelight diffusion characteristics thus obtainable.

Therefore, it is more preferable that the lower limit of such an angleof inclination θ1 is adjusted to a value of 5° or greater, and even morepreferably to a value of 10° or greater.

Furthermore, it is more preferable that the upper limit of such an angleof inclination θ1 is adjusted to a value of 60° or less, and even morepreferably to 1 value of 40° or less.

The angle of inclination θ1 means the angle of a narrower side betweenthe angles measured in a cross-section obtainable in the case of cuttinga film at a plane that is perpendicular to the film plane andorthogonally intersects the direction of extension traversing theplate-shaped regions extending in any one direction along the filmplane, the angles being formed by the normal line with respect to thefilm surface and the top of the plate-shaped regions (this definition isalso applicable to θ1 a and θ1 b that will be described below).

(3)-5 Bending

As illustrated in FIG. 5A, it is preferable that a plurality of theplate-shaped regions (11 and 12) in the louver structure 20 t as thefirst internal structure 20 constitute a bent louver structure 20 t′having a bent portion 16 at an intermediate point along the filmthickness direction.

The reason for this is that when such a bent portion is provided,incident light coming from a wide angle can be more effectivelydiffused.

It is preferable that in the bent louver structure 20 t′ illustrated inFIG. 5A, the length in the film thickness direction of the plate-shapedregions (11 and 12) in the area upper to the bent portion 16 (area onthe side irradiated with active energy radiation when the lightdiffusion control film is produced, with respect to the bent portion),that is, the length L1 a in FIG. 5B, is adjusted to a value within therange of 15 to 475 μm.

The reason for this is that if such length L1 a has a value of below 15μm, diffusion originating from the plate-shaped regions in the upperarea becomes too weak, and it may be difficult to effectively extend therange of the light diffusion characteristics. Meanwhile, as the contentof an ultraviolet absorber in the composition for a light diffusioncontrol film is larger, such a length tends to be shortened. Therefore,in other words, when it is said that such a length is excessively short,the content of the ultraviolet absorber becomes very large, and in thatcase, the possibility that shrinkage wrinkles of the film may begenerated increases when the composition for a light diffusion controlfilm is cured, so that control is made difficult. On the other hand, ifsuch length L1 a has a value of above 475 μm, the content of theultraviolet absorber becomes very small, and in that case, theplate-shaped regions in the lower area are not sufficiently formed,while there is a possibility that it may be difficult to effectivelyextend the range of the light diffusion characteristics.

Therefore, it is more preferable that in the bent louver structure, thelower limit of the length L1 a of the plate-shaped regions in the areaupper to the bent portion is adjusted to a value of 25 μm or greater,and even more preferably to a value of 30 μm or greater.

Furthermore, it is more preferable that in the bent louver structure,the upper limit of the length L1 a of the plate-shaped regions in thearea upper to the bent portion is adjusted to a value of 300 μm or less,and even more preferably to a value of 150 μm or less.

Furthermore, it is preferable that in the bent louver structure 20 t′illustrated in FIG. 5A, the length in the film thickness direction ofthe plate-shaped regions (11 and 12) in the area lower to the bentportion 16 (area on the opposite side of the above-described upper areawith respect to the bent portion), that is, the length L1 b in FIG. 5B,is adjusted to a value within the range of 15 to 475 μm.

The reason for this is that if such length L1 b has a value of below 15μm, diffusion originating from the louver structure in the lower areabecomes too weak, and it may be difficult to effectively extend therange of the light diffusion characteristics. On the other hand, it isbecause if such length L1 b has a value of above 475 μm, diffusionoriginating from the louver structure in the lower area can besufficiently obtained; however, the film thickness of the lightdiffusion control film may become excessively large.

Therefore, it is more preferable that in the bent lover structure, thelower limit of the length Lib of the plate-shaped regions in the arealower to the bent portion is adjusted to a value of 25 μm or greater,and even more preferably to a value of 30 μm or greater.

Furthermore, it is more preferable that in the bent louver structure,the upper limit of the length L1 b of the plate-shaped regions in thearea lower to the bent portion is adjusted to a value of 300 μm or less,and even more preferably to a value of 150 μm or less.

Furthermore, as illustrated in FIG. 5B, it is preferable that in thebent louver structure 20 t′, the angle of inclination θ1 a of theplate-shaped regions in the area upper to the bent portion 16 withrespect to the normal line to the film plane is adjusted to a valuewithin the range of 0° to 60°.

If such angle of inclination θ1 a has a value of above 60°, the absolutevalue of the incident angle of active energy radiation also increasestherewith. Thus, the proportion of reflection of the active energyradiation at an interface between air and the coating layer increases,and at the time of forming a louver structure, there is a need toirradiate the louver structure with active energy radiation at a higherillumination. Meanwhile, if such an angle of inclination θ1 a has anexcessively small value, it may be difficult to impart the direction ofexit (PD) to the light diffusion characteristics thus obtainable.

Therefore, it is more preferable that the lower limit of such an angleof inclination θ1 a is adjusted to a value of 2° or greater, and evenmore preferably to a value of 3° or greater.

Furthermore, it is more preferable that the upper limit of such an angleof inclination θ1 a is adjusted to a value of 45° or less, and even morepreferably to a value of 30° or less.

Furthermore, as illustrated in FIG. 5B, it is preferable that in thebent louver structure 20 t′, the angle of inclination θ1 b of theplate-shaped regions in the area lower to the bent portion 16 withrespect to the normal line to the film plane is adjusted to a valuewithin the range of 1° to 80°.

The reason for this is that when such an angle of inclination θ1 b has avalue of below 1°, even if the synergistic effect with the plate-shapedregions in the area upper to the bent portion is considered, it may bedifficult to sufficiently obtain an effect of extending the range of thelight diffusion characteristics. On the other hand, it is because ifsuch an angle of inclination θ1 b has a value of above 80°, when thesynergistic effect with the plate-shaped regions in the area upper tothe bent portion is considered, the range of the light diffusioncharacteristics can be sufficiently extended even without furtherincreasing the angle of inclination.

Therefore, it is more preferable that the lower limit of such an angleof inclination θ1 b is adjusted to a value of 5° or greater, and evenmore preferably to a value of 10° or greater.

Furthermore, it is more preferable that the upper limit of such an angleof inclination θ1 b is adjusted to a value of 60° or less, and even morepreferably to a value of 40° or less.

It is also preferable that the value of θ1 b-θ1 a in FIG. 5B is adjustedto a value of 1° or greater, more preferably to a value of 2° orgreater, and even more preferably to a value of 3° or greater.

It is preferable that the value of θ1 b-θ1 a is adjusted to a value of45° or less, more preferably to a value of 30° or less, and even morepreferably to a value of 20° or less.

As illustrated in FIG. 5B, the angle of inclination θ1 a means an angleon the narrower side between the angles formed by the normal line to thefilm plane and the top of the plate-shaped regions in the area upper tothe bent portion.

The angle of inclination θ1 b means an angle on the narrower sidebetween the angles formed by the normal line to the film plane and thetop of the plate-shaped regions in the area lower to the bent portion.

(4) Second Internal Structure

As illustrated in FIG. 2A, the second internal structure 30 in the lightdiffusion control film 10′ of the invention is an internal structure forisotropically diffusing incident light, and specifically, the secondinternal structure 30 is a columnar structure 30 s formed by arranging aplurality of pillar-shaped objects 14 having a relatively highrefractive index to stand close together in the film thickness directionwithin a region 11 having a relatively low refractive index.

The reason for this is that light incident at a predetermined angle froma light source can be uniformly diffused in advance and then introducedinto the louver structure 20 t as the first internal structure 20, ordiffused light that has become non-uniform as a result of beingpartially imparted with the direction of anisotropic diffusion (ID) orthe direction of exit (PD) by the louver structure 20 t, can beuniformly diffused again and then introduced into the next firstinternal structure 20.

As a result, as illustrated in FIG. 4, in a case in which sheets of apredetermined light diffusion control film 10′ are laminated in apredetermined mode, excellent light diffusion characteristics suitablefor a large-sized projection screen can be obtained.

(4)-1 Refractive Index

It is preferable that the relation between the refractive index of thepillar-shaped objects having a relatively high refractive index and therefractive index of the region having a relatively low refractive indexin the columnar structure, is made similar to the relation between therefractive index of the plate-shaped regions having a relatively highrefractive index and the refractive index of the plate-shaped regionshaving a relatively low refractive index in the louver structure as thefirst internal structure described above.

(4)-2 Maximum Diameter and Interval

In regard to the columnar structure 30 s illustrated in FIG. 2A, it ispreferable that the maximum diameter in a cross-section of apillar-shaped object 14 and the interval between the pillar-shapedobjects are adjusted to be similar to the value ranges for the width ofthe plate-shaped regions in the louver structure as the first internalstructure described above.

(4)-3 Thickness

It is also preferable that the thickness (length in the film thicknessdirection) of the columnar structure 30 s illustrated in FIG. 2A, thatis, L2 in FIG. 2B, is adjusted to a value within the range of 10 to 200μm.

The reason for this is that if such length L2 has a value of below 10μm, the action of uniformizing the light entering directly from a lightsource or the light diffused by the first internal structure may beachieved insufficiently. On the other hand, it is because if such lengthL2 has a value of above 200 μm, the existence proportion of the firstinternal structure becomes excessively small, and it may be difficult toeffectively extend the range of the light diffusion characteristics.

Therefore, it is more preferable that the lower limit of the length L2of the columnar structure is adjusted to a value of 20 μm or greater,and even more preferably to a value of 40 μm or greater.

Furthermore, it is more preferable that the upper limit of the length L2of the columnar structure is adjusted to a value of 150 μm or less, andeven more preferably to a value of 100 μm or less.

(4)-4 Angle of Inclination

For a reason similar to that for the angle of inclination θ1, it ispreferable that the angle of inclination θ2 of the pillar-shaped objects14 having a relatively high refractive index in the columnar structure30 s illustrated in FIG. 2B is adjusted to a value within the range of0° to 45°.

The reason for this is that when such angle of inclination θ2 has avalue within the range of 0° to 45°, the exit direction of theuniformized diffused light can be sufficiently controlled for practicaluse.

For example, in regard to digital signage, a viewer may view aprojection screen from a front position or may view the projectionscreen from a position shifted to the left or to the right or from alower position; however, when the angle of inclination θ2 has a valuewithin the range of 0° to 45°, visibility from these positions can besufficiently secured for practical use.

Meanwhile, usually, since it is assumed that a viewer views a projectionscreen from the vicinity of the front face, it is more preferable thatthe upper limit of such angle of inclination θ1 is adjusted to a valueof 30° or less, and even more preferably to a value of 10° or less.

As illustrated in FIG. 2B, it is preferable that the angles ofinclination θ2 and θ1 are inclined to the same side (including the angleof inclination of 0°), and the angles of inclination gradually increasein this order.

Furthermore, as illustrated in FIG. 5B, in a case in which the firstinternal structure 20 is a bent louver structure 20 t′, it is preferablethat the angles of inclination θ2, θ1 a, and θ1 b are inclined to thesame side (including the angle of inclination of 0°), and the angles ofinclination gradually increase in this order.

The reason for this is that as the angles of inclination graduallychange, the ranges of the light diffusion characteristics originatingfrom the respective internal structures overlap each other, and thefinal range of the light diffusion characteristics can be extendedeffectively.

Meanwhile, the angle of inclination θ2 means the angle on the narrowerside between the angles measured in a cross-section in the case ofcutting the film at a plane that is perpendicular to the film plane andcuts one entire pillar-shaped object into two along the axial line, theangles being formed by the normal line to the film surface and the topof the pillar-shaped objects.

(5) Overlapping Internal Structure

As illustrated in FIG. 2B, it is preferable that the light diffusioncontrol film 10′ has an overlapping internal structure 40 in which theposition of the upper end portion of a louver structure 20 t as thefirst internal structure 20 and the position of the lower end portion ofthe columnar structure 30 s as the second internal structure 30 overlapeach other in the film thickness direction.

The reason for this is that when the light diffusion control film 10′has an overlapping internal structure, incident light being directlytransmitted and thereby straight-traveling transmitted light beingincorporated into the diffused light can be effectively suppressed, anduniformity of the intensity of diffused light can be enhanced, ascompared to the case in which an internal structure-unformed area existsbetween the respective internal structures.

Hereinafter, the overlapping internal structure will be specificallyexplained.

(5)-1 Shape

The overlapping internal structure is not particularly limited as longas the position of the upper end portion of a louver structure as thefirst internal structure and the position of the lower end portion of acolumnar structure as the second internal structure are formed tooverlap each other in the film thickness direction.

More specifically, as illustrated in FIGS. 6A and 6B, the overlappinginternal structure 40 is desirably a structure in which an edge of anyone of the regions (12 and 14) having a relatively high refractiveindex, which originate from the louver structure 20 t as the firstinternal structure 20 and the columnar structure 30 s as the secondinternal structure 30, respectively, is incorporated into the region 11having a relatively low refractive index, which originates from therespective other one of the internal structures (30 s and 20 t).

At this time, as illustrated in FIG. 6A, the overlapping internalstructure 40 is preferably a structure in which an edge of any one ofthe regions (12 and 14) having a relatively high refractive index, whichrespectively originate from one of the two internal structures (20 t and30 s), is in contact with the vicinity of an edge of the other one ofthe regions (14 and 12) having a relatively high refractive index, whichrespectively originate from the internal structures (30 s and 20 t).

Alternatively, as illustrated in FIG. 6B, an overlapping internalstructure 40 in which the regions (12 and 14) having a relatively highrefractive index, which respectively originate from the two internalstructures (20 t and 30 s), overlap each other in a non-contact state,is also preferable.

Meanwhile, in FIGS. 6A and 6B, the plate-shaped regions 12 having arelatively high refractive index in the louver structure 20 t areindicated with solid lines, and the pillar-shaped objects 14 in thecolumnar structure 30 s are indicated with dotted lines.

(5)-2 Difference in Angle of Inclination

It is also preferable that the difference between the angles ofinclination (θ1 and θ2) of the regions (12 and 14) having a relativelyhigh refractive index, which originate from the louver structure 20 t asthe first internal structure 20 and the columnar structure 30 s as thesecond internal structure 30, respectively, illustrated in FIG. 2B isadjusted to a value of 5° or greater.

The reason for this is that the range of the light diffusioncharacteristics can be extended more effectively by adjusting such adifference in the angle of inclination to a value of 5° or greater.Meanwhile, if the value of such a difference in the angle of inclinationis an excessively large value, the ranges of the light diffusioncharacteristics attributed to the various internal structures of thelight diffusion control film thus obtainable become completelyindependent, and the overall range of the light diffusioncharacteristics of the film may not be extended efficiently.

Therefore, it is more preferable that the lower limit of such adifference in the angle of inclination is adjusted to a value of 7° orgreater, and even more preferably to a value of 10° or greater.

Furthermore, it is preferable that the upper limit of such a differencein the angle of inclination is adjusted to a value of 35° or less, andmore preferably to a value of 20° or less.

Meanwhile, when the first internal structure is a bent louver structureas illustrated in FIG. 5A, the angle of inclination θ1 described abovecan be replaced with angle of inclination θ1 a.

(5)-3 Thickness

It is also preferable that the thickness (length in the film thicknessdirection) L3 of the overlapping internal structure 40 illustrated inFIG. 2B is adjusted to a value within the range of 1 to 40 μm.

The reason for this is that if such length L3 has a value of below 1 μm,incident light is likely to be directly transmitted straight, and it maybe difficult to maintain the uniformity of the intensity of diffusedlight more stably. On the other hand, it is because if such length L3has a value of above 40 μm, the extraction efficiency for diffused lightmay be lowered. That is, in a case in which the length of theoverlapping internal structure is too long, it is expected thatbackscattering or the like occurs in that region, and this will bringabout a decrease in the extraction efficiency for diffused light.

Therefore, it is more preferable that the lower limit of the length L3of the overlapping internal structure is adjusted to a value of 3 μm orgreater, and even more preferably to a value of 5 μm or greater.

Furthermore, it is more preferable that the upper limit of the length L3of the overlapping internal structure is adjusted to a value of 35 μm orless, and even more preferably to a value of 30 μm or less.

(6) Total Film Thickness

It is preferable that the total film thickness of the light diffusioncontrol film according to the invention is adjusted to a value withinthe range of 60 to 700 μm.

The reason for this is that if the total film thickness of the lightdiffusion control film has a value of below 60 μm, the amount ofincident light that travels straight through the internal structuresincreases, and it may be difficult for the light diffusion control filmto exhibit the light diffusion characteristics. On the other hand, it isbecause if the total film thickness of the light diffusion control filmhas a value of above 700 μm, when the internal structures are formed byirradiating a composition for a light diffusion control film with activeenergy radiation, the direction of progress of photopolymerization isdiffused by the internal structures formed in the beginning, and it maybe difficult to form desired internal structures.

Therefore, it is more preferable that the lower limit of the total filmthickness of the light diffusion control film is adjusted to a value of80 μm or greater, and even more preferably to a value of 100 μm orgreater.

Furthermore, it is more preferable that the upper limit of the totalfilm thickness of the light diffusion control film is adjusted to avalue of 450 μm or less, and even more preferably to a value of 250 μmor less.

(7) Production Method

It is preferable that the light diffusion control film 10′ having thepredetermined internal structures illustrated in FIG. 2A is producedaccording to a production method including the following steps (a) to(d):

(a) a step of preparing a composition for a light diffusion controlfilm, the composition including at least two polymerizable compoundshaving different refractive indices and a photopolymerization initiator;

(b) a step of applying the composition for a light diffusion controlfilm on a process sheet and forming a coating layer;

(c) a step of subjecting the coating layer to first irradiation withactive energy radiation, forming a louver structure as a first internalstructure in the lower part of the coating layer, and also leaving aninternal structure-unformed region in the upper part of the coatinglayer; and

(d) a step of subjecting the coating layer to second irradiation withactive energy radiation and forming a columnar structure as a secondinternal structure in the internal structure-unformed region.

In the following description, such a production method will bespecifically explained with reference to the drawings.

(8)-1 Step (a): Step of Preparing Composition for Light DiffusionControl Film

Step (a) is a step of preparing a predetermined composition for a lightdiffusion control film.

More specifically, it is preferable that two polymerizable compoundshaving different refractive indices and the like are stirred under hightemperature conditions at 40° C. to 80° C., and thereby a uniform mixedliquid is prepared.

Furthermore, it is preferable to obtain a solution of the compositionfor a light diffusion control film by further adding a diluting solventas necessary, so as to obtain a desired viscosity.

In the following description, step (a) will be described morespecifically.

(i) (A) High-Refractive Index Polymerizable Compound

(i)-1 Refractive Index

It is preferable that the refractive index of a polymerizable compoundhaving a higher refractive index (hereinafter, may be referred to ascomponent (A)) between the two polymerizable compounds having differentrefractive indices, is adjusted to a value within the range of 1.5 to1.65.

The reason for this is that if the refractive index of component (A) hasa value of below 1.5, the difference between this refractive index andthe refractive index of the polymerizable compound having a lowerrefractive index (hereinafter, may be referred to as component (B))becomes too small, and it may be difficult to obtain effective lightdiffusion characteristics. On the other hand, it is because if therefractive index of component (A) has a value of above 1.65, thedifference between this refractive index and the refractive index ofcomponent (B) becomes large; however, it may be difficult for component(A) to form even an apparently miscible state with component (B).

Therefore, it is more preferable that the lower limit of the refractiveindex of the component (A) is adjusted to a value of 1.55 or greater,and even more preferably to a value of 1.56 or greater.

Furthermore, it is more preferable that the upper limit value of therefractive index of component (A) is adjusted to a value of 1.6 or less,and even more preferably to a value of 1.59 or less.

The refractive index of component (A) described above means therefractive index of component (A) before being cured by lightirradiation.

Furthermore, the refractive index can be measured according to, forexample, JIS K0062.

(i)-2 Type

The type of component (A) is not particularly limited; however, examplesinclude biphenyl (meth)acrylate, naphthyl (meth)acrylate, anthracyl(meth)acrylate, benzylphenyl (meth)acrylate, biphenyloxyalkyl(meth)acrylate, naphthyloxyalkyl (meth)acrylate, anthracyloxyalkyl(meth)acrylate, benzylphenyloxyalkyl (meth)acrylate, and compoundsobtained by partially substituting these compounds with halogen, alkyl,alkoxy, halogenated alkyl or the like.

The term “(meth)acrylic acid” means both acrylic acid and methacrylicacid.

It is more preferable that the composition for a light diffusion controlfilm includes a compound containing a biphenyl ring as component (A),and particularly, it is even more preferable that the compositionincludes a biphenyl compound represented by the following GeneralFormula (1):

wherein in General Formula (1), R¹ to R¹⁰ are independent of oneanother, and at least one of R¹ to R¹⁰ represents a substituentrepresented by the following General Formula (2), while each of theothers represents any one substituent selected from a hydrogen atom, ahydroxyl group, a carboxyl group, an alkyl group, an alkoxy group, ahalogenated alkyl group, a hydroxyalkyl group, a carboxyalkyl group, anda halogen atom.

wherein in General Formula (2), R¹¹ represents a hydrogen atom or amethyl group; the number of carbon atoms, n, represents an integer from1 to 4; and the number of repetitions, m, represents an integer from 1to 10.

Regarding the reason for this, it is speculated to be because when thecomposition for a light diffusion control film includes a biphenylcompound having a particular structure as component (A), a predetermineddifference is produced between the rates of polymerization of component(A) and component (B), the compatibility between component (A) andcomponent (B) is deteriorated to a predetermined range, and thereby thecopolymerizability between the two components can be decreased.

Furthermore, by making the refractive index of the region having arelatively high refractive index, which originates from component (A),the difference between this refractive index and the refractive index ofthe region having a relatively low refractive index, which originatesfrom component (B), can be regulated more easily to a predeterminedvalue or greater.

Specific examples of the biphenyl compound represented by GeneralFormula (1) include, as preferred examples, compounds represented by thefollowing Formulae (3) and (4):

(i)-3 Content

It is preferable that the content of component (A) in the compositionfor a light diffusion control film is adjusted to a value within therange of 25 to 400 parts by weight with respect to 100 parts by weightof component (B) that will be described below.

The reason for this is that if the content of component (A) has a valueof below 25 parts by weight, the existence ratio of component (A) withrespect to component (B) becomes small, and the width of the regionhaving a relatively high refractive index, which originates fromcomponent (A), becomes excessively small compared to the width of theregion having a relatively low refractive index, which originates fromcomponent (B), so that it may be difficult to obtain satisfactory lightdiffusion characteristics. On the other hand, it is because if thecontent of component (A) has a value of above 400 parts by weight, theexistence ratio of component (A) with respect to component (B) becomeslarge, and the width of the region having a relatively high refractiveindex, which originates from component (A), becomes excessively largecompared to the width of the region having a relatively low refractiveindex, which originates from component (B), so that conversely it may bedifficult to obtain satisfactory light diffusion characteristics.

Therefore, it is more preferable that the lower limit of the content ofcomponent (A) is adjusted to a value of 40 parts by weight or more, andeven more preferably to a value of 50 parts by weight or more, withrespect to 100 parts by weight of component (B).

Furthermore, it is more preferable that the upper limit of the contentof component (A) is adjusted to a value of 300 parts by weight or less,and even more preferably to a value of 200 parts by weight or less, withrespect to 100 parts by weight of component (B).

(ii) (B) Low-Refractive Index Polymerizable Compound

(ii)-1 Refractive Index

It is preferable that the refractive index of component (B), that is,the polymerizable compound having a lower refractive index between thetwo polymerizable compounds having two different refractive indices, isadjusted to a value within the range of 1.4 to 1.5.

The reason for this is that if the refractive index of component (B) hasa value of below 1.4, the difference between this refractive index andthe refractive index of component (A) becomes large; however, thecompatibility with component (A) may be so deteriorated that it may bedifficult for the components to form predetermined internal structures.On the other hand, it is because if the refractive index of component(B) has a value of above 1.5, the difference between this refractiveindex and the refractive index of component (A) becomes too small, andit may be difficult to obtain desired light diffusion characteristics.

Therefore, it is more preferable that the lower limit of the refractiveindex of component (B) is adjusted to a value of 1.45 or greater, andeven more preferably to a value of 1.46 or greater.

Furthermore, it is more preferable that the upper limit of therefractive index of component (B) is adjusted to a value of 1.49 orless, and even more preferably to a value of 1.48 or less.

The refractive index of component (B) described above means therefractive index of component (B) before being cured by lightirradiation.

Furthermore, the refractive index can be measured according to, forexample, JIS K0062.

It is also preferable that the difference between the refractive indexof component (A) and the refractive index of component (B) as describedabove is adjusted to a value of 0.01 or greater.

The reason for this is that if such a difference in the refractive indexhas a value of below 0.01, since the angle range in which totalreflection of incident light occurs within the predetermined internalstructures is narrowed, the range of the light diffusion characteristicsmay become excessively narrow. On the other hand, if such a differencein the refractive index has an excessively large value, thecompatibility between component (A) and component (B) may be sodeteriorated that it may be difficult for the components to formpredetermined internal structures.

Therefore, it is more preferable that the lower limit of the differencebetween the refractive index of component (A) and the refractive indexof component (B) is adjusted to a value of 0.05 or greater, and evenmore preferably to a value of 0.1 or greater.

Furthermore, it is more preferable that the upper limit of thedifference between the refractive index of component (A) and therefractive index of component (B) is adjusted to a value of 0.5 or less,and even more preferably to a value of 0.2 or less.

The refractive indices of component (A) and component (B) as used hereinmean the refractive indices of component (A) and component (B) beforebeing cured by light irradiation.

(ii)-2 Type

The type of component (B) is not particularly limited; however, examplesinclude urethane (meth)acrylate, a (meth)acrylic polymer having a(meth)acryloyl group in a side chain, a (meth)acryloyl group-containingsilicone resin, and an unsaturated polyester resin. Particularly,urethane (meth)acrylate is preferred.

The reason for this is that when urethane (meth)acrylate is used, thedifference between the refractive index of the region having arelatively high refractive index, which originates from component (A),and the refractive index of the region having a relatively lowrefractive index, which originates from component (B), can be regulatedmore easily, and also, the fluctuation in the refractive index of theregion having a relatively low refractive index, which originates fromcomponent (B), can be effectively suppressed, so that a light diffusioncontrol film having predetermined internal structures can be obtainedmore efficiently.

Meanwhile, the term (meth)acrylate means both acrylate and methacrylate.

(iii) Photopolymerization Initiator

It is preferable that if desired, a photopolymerization initiator ascomponent (C) is incorporated into the composition for a light diffusioncontrol film.

The reason for this is that when a photopolymerization initiator isincorporated, the predetermined internal structures can be formedefficiently at the time of irradiating the composition for a lightdiffusion control film with active energy radiation.

Here, the photopolymerization initiator refers to a compound thatgenerates a radical species when irradiated with active energy radiationsuch as ultraviolet radiation.

Examples of such a photopolymerization initiator include benzoin,benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether,benzoin n-butyl ether, benzoin isobutyl ether, acetophenone,dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone,2,2-diethoxy-2-phenylacetophenone,2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenylketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one,4-(2-hydroxyethoxy)phenyl 2-(hydroxyl-2-propyl) ketone, benzophenone,p-phenylbenzophenone, 4,4-diethylaminobenzophenone,dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone,2-tertiary butylanthraquinone, 2-aminoanthraquinone,2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone,2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyl dimethylketal, acetophenone dimethyl ketal, a p-dimethylaminebenzoic acid ester,and an oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propane].These compounds may be used singly, or two or more kinds thereof may beused in combination.

In regard to the content in the case of incorporating aphotopolymerization initiator, it is preferable that the content isadjusted to a value within the range of 0.2 to 20 parts by weight, morepreferably to a value within the range of 0.5 to 15 parts by weight, andeven more preferably to a value within the range of 1 to 10 parts byweight, with respect to 100 parts by weight of the total amount ofcomponent (A) and component (B).

(iv) Ultraviolet Absorber

(iv)-1 Type

Furthermore, it is preferable that the composition for a light diffusioncontrol film includes an ultraviolet absorber as component (D).

The reason for this is that when an ultraviolet absorber is included ascomponent (D), upon irradiating with active energy radiation, activeenergy radiation having a predetermined wavelength can be selectivelyabsorbed to a predetermined extent.

It is because as a result, a bend may be produced in the louverstructure as the first internal structure formed in the film, withoutinhibiting curing of the composition for a light diffusion control film.

Here, at the present moment, the specific mechanism of how anultraviolet absorber generates a bend in the louver structure as thefirst internal structure that is formed within the film, has not beensufficiently elucidated.

However, the mechanism described below is speculated to be applicable.

That is, it has been recognized that as the amount of addition of theultraviolet absorber is smaller, the bending angle becomes smaller, andthe range of the light diffusion characteristics tends to diminish.

Furthermore, it has been recognized that as the ultraviolet absorber hasa peak at a site closer to the wavelength of 365 nm, which is the mainwavelength of high pressure mercury lamps, a bend is produced with asmall amount of addition of the ultraviolet absorber.

Therefore, it is speculated that as much as the wavelength of theultraviolet radiation emitted from a high pressure mercury lamp iscontrolled by the ultraviolet absorber, that is, as much as theintensity ratio of various wavelengths in the ultraviolet radiationemitted from a high pressure mercury lamp changes, the progress ofpolymerization toward the lower part in the film thickness direction ofthe coating layer is delayed, and there occurs a change in the directionof progress of polymerization at a depth at which polymerization hasprogressed to a certain extent.

Meanwhile, regarding the factor that changes the direction of progressof polymerization, the difference between the refractive indices ofcomponent (A) and component (B) may be considered; however, in such adifference in the refractive index, a bend that is actually recognizableis not produced according to calculations.

Furthermore, it is preferable that component (D) is at least oneselected from the group consisting of a hydroxyphenyltriazine-basedultraviolet absorber, a benzotriazole-based ultraviolet absorber, abenzophenone-based ultraviolet absorber, and a hydroxybenzoate-basedultraviolet absorber.

The reason for this is that when such an ultraviolet absorber is used,since a bend can be produced more clearly in the louver structure as thefirst internal structure, the range of the light diffusioncharacteristics in the light diffusion control film thus obtainable canbe extended more effectively.

That is, it is because it has been confirmed that when an ultravioletabsorber having a peak at a site closer to the wavelength of 365 nm,which is the main wavelength of high pressure mercury lamps, is used, abend is produced with a small amount of addition of the ultravioletabsorber.

(iv)-2 Absorption Wavelength

It is also preferable that component (D) has an absorption peak forlight having a wavelength of 330 to 380 nm.

The reason for this is that when the absorption peak of component (D) isin this range, component (D) can efficiently absorb energy at 365 nm,which is the main wavelength of high pressure mercury lamps, andthereby, a louver structure having a bend can be efficiently formed inthe light diffusion control film thus obtainable.

On the other hand, many of ultraviolet absorbers having absorption peaksat wavelengths of below 330 nm exhibit small absorption at 365 nm.Therefore, even if such an ultraviolet absorber is used, a louverstructure having a sufficient bend may not be formed in the lightdiffusion control film thus obtainable.

Meanwhile, many of ultraviolet absorbers having absorption peaks atwavelengths of above 380 nm reliably exhibit absorption at 365 nm aswell. However, since many of such ultraviolet absorbers exhibitabsorption in the entire ultraviolet region, in order to realizeabsorption at 365 nm, it will be necessary to increase the amount ofaddition. As a result, when an ultraviolet absorber having an absorptionpeak at a wavelength of above 380 nm is used, curing per se of the lightdiffusion control film may be inhibited.

Therefore, it is more preferable that the absorption peak for component(D) is adjusted to a wavelength value within the range of 335 to 375 nm,and even more preferably to a wavelength value within the range of 340to 370 nm.

(iv)-3 Content

It is preferable that the content of component (D) in the compositionfor a light diffusion control film is adjusted to a value of below 2parts by weight (provided that 0 parts by weight is excluded) withrespect to the total amount (100 parts by weight) of component (A) andcomponent (B).

The reason for this is that when the content of component (D) isadjusted to a value within such a range, a bend can be produced in thelouver structure as the first internal structure formed within the film,without inhibiting curing of the composition for a light diffusioncontrol film, and thereby, the range of the light diffusioncharacteristics of the light diffusion control film thus obtainable canbe extended effectively.

That is, it is because if the content of component (D) has a value of 2parts by weight or more, curing of the composition for a light diffusioncontrol film may be inhibited, and shrinkage wrinkles may be generatedat the film surface, or the composition may not be cured at all. On theother hand, if the content of component (D) is excessively small, it maybe difficult to produce a sufficient bend in the louver structure as thefirst internal structure formed within the film.

Therefore, it is more preferable that the lower limit of the content ofcomponent (D) is adjusted to a value of 0.01 parts by weight or greater,and even more preferably to a value of 0.02 parts by weight or greater,with respect to the total amount (100 parts by weight) of component (A)and component (B).

Furthermore, it is more preferable that the upper limit of the contentof component (D) is adjusted to a value of 1.5 parts by weight or less,and even more preferably to a value of 1 part by weight or less, withrespect to the total amount (100 parts by weight) of component (A) andcomponent (B).

(v) Other Additives

Furthermore, other additives can be added to the composition for a lightdiffusion control film as appropriate, to the extent that the effects ofthe invention are not impaired.

Examples of the other additives include an oxidation inhibitor, anantistatic agent, a polymerization accelerator, a polymerizationinhibitor, an infrared absorber, a plasticizer, a diluting solvent, anda leveling agent.

It is preferable that the content of the other additives is generallyadjusted to a value within the range of 0.01 to 5 parts by weight withrespect to the total amount (100 parts by weight) of component (A) andcomponent (B).

(8)-2 Step (b): Step of Applying Composition for Light Diffusion ControlFilm

Step (b) is, as illustrated in FIG. 7A, a step of applying thecomposition for a light diffusion control film thus prepared on aprocess sheet 2 and thereby forming a coating layer 1.

Regarding the process sheet, plastic films and paper can both be used.

Among these, examples of plastic films include polyester-based filmssuch as a polyethylene terephthalate film; polyolefin-based films suchas a polyethylene film and a polypropylene film; cellulose-based filmssuch as a triacetylcellulose film; and polyimide-based films.

Examples of paper include glassine paper, coated paper, and laminatedpaper.

In consideration of the steps that will be described below, the processsheet 2 is preferably a film having excellent dimensional stabilityagainst heat or active energy radiation.

Preferred examples of such a film include, as described above,polyester-based films, polyolefin-based films, and polyimide-basedfilms.

In regard to the process sheet, it is preferable to provide a releaselayer on a surface of the process sheet, the surface being on the sideof the surface coated with the composition for a light diffusion controlfilm, in order to make it easier to release the light diffusion controlfilm thus obtained, from the process sheet after photocuring.

Such a release layer can be formed using a conventionally known releaseagent, such as a silicone-based release agent, a fluorine-based releaseagent, an alkyd-based release agent, or an olefin-based release agent.

It is preferable that the thickness of the process sheet is adjusted toa value within the range of, usually, 25 to 200 μm.

Regarding the method of applying the composition for a light diffusioncontrol film on the process sheet, for example, the coating process canbe carried out by a conventionally known method such as, for example, aknife coating method, a roll coating method, a bar coating method, ablade coating method, a die coating method, or a gravure coating method.

At this time, it is preferable that the thickness of the coating layeris adjusted to a value within the range of 60 to 700 μm.

(8)-3 Step (c): Step of Performing First Irradiation with Active EnergyRadiation

Step (c) is, as illustrated in FIG. 7B, a step of subjecting the coatinglayer 1 to first irradiation with active energy radiation, forming alouver structure 20 t as a first internal structure in the lower part ofthe coating layer 1, and also leaving an internal structure-unformedregion 1′ in the upper part of the coating layer 1.

That is, as illustrated in FIG. 7B, the coating layer 1 formed on theprocess sheet is irradiated with light 70′ that is substantiallyparallel light when viewed from one direction and is seen asnon-parallel random light when viewed from another direction.

Such light 70′ can be emitted using, for example, a linear light source125, and in this case, the light is seen as substantially parallel lightwhen viewed from the axial direction of the linear light source 125, andis seen as non-parallel random light when viewed from another direction.

Regarding the angle of irradiation of the emitted light, as illustratedin FIG. 8, it is preferable that the angle of irradiation θx in the caseof defining the angle of the normal line to the surface of the coatinglayer 1 as 0°, is adjusted to a value within the range of, usually, −80°to 80°.

The reason for this is that when the angle of irradiation has a valueout of the range of −80° to 80°, the influence of reflection at thesurface of the coating layer 1 or the like increases, and it may bedifficult to sufficiently form a louver structure.

The arrow MD in FIG. 8 shows the direction of travel of the coatinglayer.

Furthermore, it is preferable to use ultraviolet radiation as theemitted light.

The reason for this is that in the case of an electron beam, since therate of polymerization is very fast, component (A) and component (B) donot sufficiently undergo phase separation during the process ofpolymerization, and it may be difficult for the components to form alouver structure. On the other hand, it is because when compared withvisible light or the like, since ultraviolet radiation is associatedwith a rich variety of ultraviolet-curable resin that is cured whenirradiated with ultraviolet radiation, or a rich variety ofphotopolymerization initiators that can be used, the width of selectionfor component (A) and component (B) can be widened.

Furthermore, regarding the conditions for the first irradiation withactive energy radiation, it is preferable that the peak illuminance atthe surface of the coating layer is adjusted to a value within the rangeof 0.1 to 3 mW/cm².

The reason for this is that if such a peak illuminance has a value ofbelow 0.1 mW/cm², a sufficient internal structure-unformed region can besecured; however, it may be difficult to form a clear louver structure.On the other hand, if such a peak illuminance has a value of above 3mW/cm², even if an internal structure-unformed region exists, it isspeculated that the curing reaction in the relevant region proceedsexcessively, and thus, in the step of second irradiation with activeenergy radiation that will be described below, it may be difficult tosatisfactorily form a columnar structure as the second internalstructure.

Therefore, it is more preferable that the lower limit of the peakilluminance at the surface of the coating layer in the first irradiationwith active energy radiation is adjusted to a value of 0.3 mW/cm² orgreater, and even more preferably to a value of 0.5 mW/cm² or greater.

Furthermore, it is more preferable that the upper limit of the peakilluminance at the surface of the coating layer in the first irradiationwith active energy radiation is adjusted to a value of 2 mW/cm² or less,and even more preferably to a value of 1.5 mW/cm² or less.

Furthermore, it is preferable that the cumulative amount of light at thesurface of the coating layer in the first irradiation with active energyradiation is adjusted to a value within the range of 5 to 100 mJ/cm².

The reason for this is that if such a cumulative amount of light has avalue of below 5 mJ/cm², it may be difficult to sufficiently extend thelouver structure from the upper part toward the lower part, or thelouver structure may change when a columnar structure is formed as thesecond internal structure. On the other hand, if such a cumulativeamount of light has a value of above 100 mJ/cm², curing may proceedexcessively in the internal structure-unformed region, and it may bedifficult to satisfactorily form a columnar structure as the secondinternal structure in the step for second irradiation with active energyradiation that will be described below.

Therefore, it is more preferable that the lower limit of the cumulativeamount of light at the surface of the coating layer in the firstirradiation with active energy radiation is adjusted to a value of 7mJ/cm² or greater, and even more preferably to a value of 10 mJ/cm² orgreater.

Furthermore, it is more preferable that the upper limit of thecumulative amount of light at the surface of the coating layer in thefirst irradiation with active energy radiation is adjusted to a value of50 mJ/cm² or less, and even more preferably to a value of 30 mJ/cm² orless.

Furthermore, from the viewpoint of stably forming a louver structurewhile maintaining mass productivity, it is preferable that when thefirst irradiation with active energy radiation is performed, the coatinglayer formed on the process sheet is moved at a rate within the range of0.1 to 10 m/min.

Particularly, it is more preferable that the coating layer is moved at arate of 0.2 m/min or grater, and it is more preferable that the coatinglayer is moved at a rate of 3 m/min or less.

From the viewpoint of efficiently leaving an internal structure-unformedregion, it is preferable that the step of performing first irradiationwith active energy radiation is carried out in an atmosphere containingoxygen (preferably, in an air atmosphere).

The reason for this is that when the first irradiation with activeenergy radiation is performed in an atmosphere containing oxygen, aninternal structure-unformed region can be stably left in the upper partof the coating layer by utilizing the influence of oxygen inhibition,while a louver structure is efficiently formed in the lower part of thecoating layer.

That is, it is because if the first irradiation with active energyradiation is performed not in an atmosphere containing oxygen but in anoxygen-free atmosphere containing no oxygen, a louver structure may beformed continuously almost to the outermost surface of the film, withoutleaving an internal structure-unformed region in the upper part of thefilm.

The phrase “in an atmosphere containing oxygen” means conditions inwhich the top face of the coating layer is in direct contact with a gascontaining oxygen, such as air, and above all, the phrase “in an airatmosphere” means conditions in which the top face of the coating layeris in direct contact with air.

Therefore, performing the first irradiation with active energy radiationin a state in which the top face of the coating layer is exposeddirectly to air, without performing particular means such as laminatinga film on the top face of the coating layer or purging with nitrogen,corresponds to the first irradiation with active energy radiation “in anair atmosphere”.

(8)-4 Step (d): Step of Performing Second Irradiation with Active EnergyRadiation

Step (d) is, as illustrated in FIG. 7C, a step of further subjecting thecoating layer 1 to second irradiation with active energy radiation, andforming a columnar structure 30 s as the second internal structure 30 inthe internal structure-unformed region 1′.

That is, as illustrated in FIG. 7C, the coating layer 1 formed on theprocess sheet is irradiated with parallel light 60 having a high degreeof parallelism of light rays as the emitted light.

Specifically, it is preferable that the degree of parallelism of theemitted light is adjusted to a value of 10° or less.

The reason for this is that when the degree of parallelism of theemitted light is adjusted to a value within such a range, a columnarstructure formed by arranging a plurality of pillar-shaped objects tostand close together at a certain angle of inclination with respect tothe film thickness direction can be formed efficiently and stably.

Therefore, it is more preferable that the degree of parallelism ofparallel light is adjusted to a value of 5° or less, and even morepreferably to a value of 2° or less.

Regarding the conditions for the second irradiation with active energyradiation, it is preferable that the peak illuminance at the surface ofthe coating layer is adjusted to a value within the range of 0.1 to 20mW/cm².

The reason for this is that if such a peak illuminance has a value ofbelow 0.1 mW/cm², it may be difficult to form a clear columnar structureas the second internal structure. On the other hand, it is because ifsuch an illuminance has a value of above 20 mW/cm², it is speculatedthat the curing rate becomes too fast, and a columnar structure as thesecond internal structure may not be formed effectively.

Therefore, it is more preferable that the lower limit of the peakilluminance at the surface of the coating layer in the secondirradiation with active energy radiation is adjusted to a value of 0.3mW/cm² or greater, and even more preferably to a value of 0.5 mW/cm² orgreater.

Furthermore, it is more preferable that the upper limit of the peakilluminance at the surface of the coating layer in the secondirradiation with active energy radiation is adjusted to a value of 10mW/cm² or less, and even more preferably to a value of 5 mW/cm² or less.

Furthermore, it is preferable that the cumulative amount of light at thesurface of the coating layer in the second irradiation with activeenergy radiation is adjusted to a value within the range of 5 to 300mJ/cm².

The reason for this is that if such a cumulative amount of light has avalue of below 5 mJ/cm², it may be difficult to sufficiently extend thecolumnar structure as the second internal structure from the upper parttoward the lower part. On the other hand, if such a cumulative amount oflight has a value of above 300 mJ/cm², the film thus obtainable may becolored.

Therefore, it is more preferable that the lower limit of the cumulativeamount of light at the surface of the coating layer in the secondirradiation with active energy radiation is adjusted to a value of 10mJ/cm² or greater, and even more preferably to a value of 20 mJ/cm² orgreater.

Furthermore, it is more preferable that the upper limit of thecumulative amount of light at the surface of the coating layer in thesecond irradiation with active energy radiation is adjusted to a valueof 200 mJ/cm² or less, and even more preferably to a value of 150 mJ/cm²or less.

Furthermore, it is preferable that the second irradiation with activeenergy radiation is performed in an oxygen-free atmosphere.

The reason for this is that when the second irradiation with activeenergy radiation in an oxygen-free atmosphere, a columnar structure asthe second internal structure can be formed efficiently by suppressingthe influence of oxygen inhibition on the internal structure-unformedregion obtained by the first irradiation with active energy radiation.

That is, it is because if the second irradiation with active energyradiation is performed not in an oxygen-free atmosphere but in an oxygenatmosphere, when irradiation is performed at a high illuminance, acolumnar structure as the second internal structure may be formed at avery shallow position in the vicinity of the surface; however, thedifference in the refractive index required for light diffusion may notbe obtained. Furthermore, it is because when irradiation is performed ata low illuminance, a columnar structure as the second internal structuremay not be formed in the internal structure-unformed region under theinfluence of oxygen inhibition.

Meanwhile, the phrase “in an oxygen-free atmosphere” means conditions inwhich the top face of the coating layer is not in direct contact with anoxygen atmosphere, or an atmosphere containing oxygen.

Therefore, for example, performing the second irradiation with activeenergy radiation in a state in which a film is laminated on the top faceof the coating layer or nitrogen purge has been performed by replacingair with nitrogen gas, corresponds to the second irradiation with activeenergy radiation “in an oxygen-free atmosphere”.

As described above, when a louver structure as the first internalstructure and a columnar structure as the second internal structure areformed by the first irradiation with active energy radiation and thesecond irradiation with active energy radiation, respectively, thecombination of angles of inclination in the regions having a relativelyhigh refractive index in the respective internal structures can beeasily regulated.

That is, the combination of the angles of inclination in the regionshaving a relatively high refractive index in the various internalstructures can be easily regulated only by appropriately regulating theangles of irradiation in the respective cases of irradiation with activeenergy radiation.

(9) Other Embodiments

The light diffusion control film having a predetermined internalstructure according to the invention has been explained primarily bytaking the light diffusion control film 10′ illustrated in FIG. 2A as anexample; however, the light diffusion control film having apredetermined internal structure according to the invention is notintended to be limited to this.

For example, the light diffusion control film 10 having a columnarstructure only as illustrated in FIG. 1 is also acceptable.

Furthermore, the light diffusion control film may also be the lightdiffusion control film 10″ illustrated in FIG. 9A, in which the firstinternal structure 20 and the second internal structure 30 are bothcolumnar structures (20 s and 30 s).

It is more preferable that such a light diffusion control film 10″ is,as illustrated in FIG. 9B, a bent columnar structure 20 s′ in whichpillar-shaped objects that constitute the first internal structure 20have a bent portion.

The light diffusion control film 10″ may also be a light diffusioncontrol film 10′″ as illustrated in FIG. 9C, in which the first internalstructure 20 is a predetermined internal structure 20 u obtained byarranging flaky objects having a relatively high refractive index in aregion having a relatively low refractive index, and the second internalstructure 30 is a columnar structure 30 s.

It is more preferable that such a light diffusion control film 10′″ is,as illustrated in FIG. 9D, a predetermined bent internal structure 20 u′in which the flaky objects that constitute the first internal structure20 of the film have a bent portion.

Meanwhile, the details of the light diffusion control films illustratedin FIGS. 9A to 9D are equivalent to the details of the light diffusioncontrol film illustrated in FIG. 2A.

2. Light Diffusion Control Plate

(1) Light Diffusion Characteristics

The light diffusion control plate according to the invention comprises alight diffusion control film having an internal structure including aplurality of regions having a relatively high refractive index in aregion having a relatively low refractive index within the film asdescribed above, in which as illustrated in FIGS. 10A to 10C, when afirst direction D1 and a second direction D2 orthogonally intersectingeach other are assumed to be on the surface of the light diffusioncontrol plate, and when the incident angle of the light incident to thelight diffusion control plate is defined such that an angle parallel tothe normal line to the surface of the light diffusion control plate isdefined as 0°, in a case in which the luminance of diffused lightobtainable when light is incident on the intersection point of theorthogonally intersecting first direction D₁ and second direction D₂ atan incident angle of θy=θ′y=0° is designated as L₀ (cd/m²); theluminance of diffused light obtainable when light is incident on theintersection point of the orthogonally intersecting first direction D₁and second direction D₂ at an incident angle θy varying in the range of−30° to 30° (θ′y=0°) along the first direction D1 is designated as L₁(cd/m²); and the luminance of diffused light obtainable when light isincident on the intersection point of the orthogonally intersectingfirst direction D₁ and second direction D₂ at an incident angle θ′yvarying in the range of 0° to 30° (θy=0°) along the second direction D2is designated as L₂ (cd/m²), there exist the first direction D₁ and thesecond direction D₂ as illustrated in FIGS. 11A and 11B, in which L₀,L₁, and L₂ always satisfy the following relational expressions (1) and(2):L ₁≥0.25×L ₀  (1)L ₂≥0.25×L ₀  (2)

The reason for this is that when the relational expressions (1) and (2)are satisfied, incident light coming from a wide range of angles in thetransverse direction and the vertical direction can be effectivelydiffused, and even in a case in which the light diffusion control plateis applied to a large-sized screen, a wide viewing angle in thetransverse direction as well as the vertical direction can be obtained.

That is, it is because if the value of L₁ is a value of below 0.25×L₀,it is difficult to sufficiently diffuse light in the front direction ofthe projection screen even in a case in which the incident angle θy isbelow 30°, and thus it is difficult to apply the light diffusion controlplate to a large-sized screen, for which the incident angle θy shouldhave a large value.

Similarly, if the value of L₂ is a value of below 0.25×L₀, it isdifficult to sufficiently diffuse light in the front direction of theprojection screen even in a case in which the incident angle θ′y isbelow 30°, and thus it is difficult to apply the light diffusion controlplate to a large-sized screen, for which the incident angle θ′y shouldhave a large value.

Therefore, it is more preferable that the following relationalexpressions (1′) and (2′) are satisfied, and it is even more preferablethat the following relational expressions (1″) and (2″) are satisfied.

Meanwhile, L₀, L₁, L₂, and L₃(−30°) that will be described below meanluminances measured in the front direction of the light diffusioncontrol plate.

The method for measuring luminance will be described in the Examples.

FIG. 10A is a plan view of the light diffusion control plate; FIG. 10Bis a lateral view obtained as the light diffusion control plate of FIG.10A is viewed along the direction of arrow X; and FIG. 10C is a lateralview obtained as the light diffusion control plate is viewed along thedirection of arrow Y.L ₁≥0.3×L ₀  (1′)L ₂≥0.3×L ₀  (2′)L ₁≥0.35×L ₀  (1″)L ₂≥0.35×L ₀  (2″)

According to the invention, the first direction D₁ may be takenarbitrarily on the surface of the light diffusion control plate.

Therefore, any combination of the first direction D₁ and the seconddirection D₂ that orthogonally intersects the first direction D1 can beunlimitedly selected within the azimuthal angle of 360° within thesurface of the light diffusion control plate; however, in a case inwhich even only one of the combinations satisfies the relationalexpressions (1) and (2), the combination of the directions is includedin the scope of the invention.

When the first direction D₁ and the second direction D₂ are defined tobe the same directions as the direction of exit (PD) in the lightdiffusion control film that constitutes the light diffusion controlplate, or directions in the vicinity thereof, the relational expressions(1) and (2) may be satisfied more easily.

Regarding the positive and negative of the incident angle θy, asillustrated in FIG. 10B, the case of opening the incident angle alongthe first direction D₁ from the state of 0° is considered as positive,and the case of opening the incident angle in the opposite direction isconsidered as negative.

Similarly, regarding the positive and negative of the incident angleθ′y, as illustrated n FIG. 10C, the case of opening the incident anglealong the second direction D₂ from the state of 0° is considered aspositive, and the case of opening the angle in the opposite direction isconsidered as negative.

In a case in which the luminance of the diffused light obtainable whenlight is incident on the intersection point of the orthogonallyintersecting first direction D₁ and second direction D₂, which aredirections along the surface, at an incident angle of −30° along thesecond direction D₂ is designated as L₃(−30°) (cd/m³), it is preferablethat L₃(−30°) satisfies the following relational expression (3):L ₃(−30°)<0.7×L ₀  (3)

The reason for this is that even when the light diffusion control plateis configured as such, incident light coming from a wide range of anglesin the transverse direction and the vertical direction can beeffectively diffused, without any kind of limitations on the useapplications of the projection screen.

That is, it is because in a projection screen, there is usually a needto effectively diffuse incident light coming from a wide angle in boththe rightward direction and the leftward direction in the transversedirection; however, the projection screen can be sufficientlypracticalized as long as the projection screen can effectively diffuseincident light coming from a wide angle in any one direction between theupward direction and the downward direction in the vertical direction.

That is, for example, in the case of using the projection screen as ahorizontally long rectangular-shaped digital signage installed at therooftop of a building, D₁ is made coincident with the horizontaldirection, while D₂ is made coincident with the vertical direction, andthe projection screen is installed in a direction in which incidentlight coming from above can be diffused effectively.

Then, a projector that serves as a light source is installed upper tothe center in the transverse direction and the center in the verticaldirection of the projection screen, viewing from the front side, theright and left sides, and the lower side of the projection screen ismade possible.

In contrast, when it is attempted to diffuse incident light coming froman angle that is not necessary, the brightness of the displayed imagestends to be easily lowered.

However, when more sheets of the light diffusion control film arefurther laminated, it is also possible to diffuse incident light comingfrom all angles.

From the reason described above, it is more preferable that thefollowing relational expression (3′) is satisfied, and it is even morepreferable that the following relational expression (3″) is satisfied.L ₃(−30°)<0.5×L ₀  (3′)L ₃(−30°)<0.2×L ₀  (3″)

Furthermore, for similar reasons, it is more preferable that L3(−30°)satisfies the following relational expressions (4) to (6):L ₃(−30°)<L ₁(30°)  (4)L ₃(−30°)<L ₁(−30°)  (5)L ₃(−30°)<L ₂(30°)  (6)

In regard to the light diffusion control plate, it is preferable thatthe transmission gain obtainable when the incident angle is set to 0° isadjusted to a value of 0.8 or greater.

The reason for this is that when the transmission gain is adjusted to avalue of 0.8 or greater, incident light coming from a wide range ofangles in the transverse direction and the vertical direction can beeffectively diffused while the brightness of the images displayed ismaintained effectively.

That is, if it is intended to simply diffuse the incident light comingfrom a wide angle, even a microparticle-dispersed type light diffusionfilm can also be realized.

Alternately, laminating at random a large number, such as five sheets ormore, of a light diffusion control film may also be realized.

However, in this case, since the angle of the incident light suppliedfor diffusion, the exit direction of diffused light, and the like arenot controlled, there is a problem that certain incident light only isdiffused excessively, and the displayed images become dim.

Therefore, from the viewpoint of suppressing such a problem, it is morepreferable that the transmission gain obtainable at the time of settingthe incident angle to 0° is adjusted to a value of 1.5 or greater, andeven more preferably to a value of 1.9 or greater.

Meanwhile, if the transmission gain becomes excessively large, the rangeof the light diffusion characteristics may become excessively narrow, itmay be difficult for the light diffusion control plate to effectivelydiffuse incident light from a wide angle, and furthermore, it may bedifficult for the light diffusion control plate to satisfy therelational expressions (1) and (2).

Therefore, it is preferable that the upper limit of the transmissiongain obtainable at the time of setting the incident angle to 0° isadjusted to a value of 5 or less, more preferably to a value of 3 orless, and even more preferably to a value of 2.5 or less.

The transmission gain is an index indicating that relatively how largeis the intensity of light in the front direction that has been diffusedby a light diffusion control plate, compared to the case in which thelight in the front direction is completely diffused.

Furthermore, the method for measuring the transmission gain will bedescribed in the Examples.

(2) Mode

It is also preferable that the light diffusion control plate is obtainedby laminating a plurality of sheets of a light diffusion control film,and the number of laminated sheets of the light diffusion control filmis adjusted to 4 or less.

The reason for this is that when the light diffusion control plate isconfigured as such, the occurrence of image blurring can be suppressed,and incident light coming from a wide range of angles in the transversedirection and the vertical direction can be diffused effectively withoutexcessively lowering the production efficiency.

That is, for example, as illustrated in FIG. 4, it is because whensheets of a predetermined light diffusion control film are laminated ina predetermined mode, the process in which diffused light that has beendiffused by a certain internal structure is diffused by the nextinternal structure is repeated, and as a result, satisfactory lightdiffusion characteristics for a projection screen can be obtained.

Furthermore, lamination of sheets of the light diffusion control filmmay be carried out by any lamination method such as lamination by meansof a pressure-sensitive adhesive, lamination by means of an adhesive, orlamination based on autohesion properties without using any adhesive;however, adhesion by means of a pressure-sensitive adhesive isparticularly preferable.

Examples of a pressure-sensitive adhesive that is suitably used includeacrylic, urethane-based, rubber-based, epoxy-based, silicone-based, andpolyester-based pressure-sensitive adhesives. The thickness of thepressure-sensitive adhesive layer is preferably adjusted to a valuewithin the range of 2 to 200 μm, and more preferably to a value withinthe range of 5 to 50 μm.

Furthermore, in a case in which a light diffusion control film of a typehaving a columnar structure s the second internal structure asillustrated in FIG. 2A, FIG. 5A, and FIGS. 9A to 9D is used as the lightdiffusion control film, it is preferable that a plurality of sheets ofthe light diffusion control film are laminated such that incident lightcoming from a projector enters the respective light diffusion controlfilms through the side of the columnar structure as the second internalstructure. The reason for this is that when the light diffusion controlplate is configured as such, the incident light coming from a projectorcan be diffused more uniformly.

That is, it is because when light is perpendicularly incident throughthe columnar structure side, a wide diffusion region can be efficientlyobtained, whereas when light enters through the louver structure side,since linear anisotropic diffusion occurs first, and then only the lightof the portion overlapping with the diffusion region of the columnarstructure is isotropically diffused into a circular shape, it may bedifficult to stably extend the range of the light diffusioncharacteristics.

Furthermore, in a case in which a light diffusion control film of a typehaving a columnar structure as the second internal structure asillustrated in FIG. 2A, FIG. 5A, and FIGS. 9A to 9D is used as the lightdiffusion control film, it is preferable that, as illustrated in FIG. 4,a plurality of the light diffusion control film are composed of first tothird light diffusion control films having the same configuration, andalso, the first to third light diffusion control films are laminatedsuch that the directions of exit (PD) of the first to third lightdiffusion control films are respectively different from one another.

The reason for this is that when the light diffusion control plate isconfigured as such, as explained in the section “Light diffusion controlfilm” using FIG. 4, incident light coming from a wide range of angles inthe vertical direction and the transverse direction within the plane ofthe projection screen can be diffused effectively.

Furthermore, as illustrated in FIG. 4, in a case in which the projectionscreen is installed parallel to the vertical direction, it is preferablethat a first light diffusion control film having a downward direction ofexit (PD), a second light diffusion control film having a lateraldirection of exit (PD), and a third light diffusion control film havinga direction of exit (PD) that is the opposite direction of that of thesecond light diffusion control film, are laminated in order from theside where incident light coming from projector enters the projectionscreen.

The reason for this is that when the light diffusion control plate isconfigured as such, incident light coming from a wide range of angles inthe downward direction and the rightward and leftward directions in theprojection screen can be diffused more effectively, as explained in thesection “Light diffusion control film” using FIG. 4.

It is also preferable that as illustrated in FIG. 1 as a fourth lightdiffusion control film, a light diffusion control film having a columnarstructure only as the internal structure is further laminated on asurface of the third light diffusion control film, the surface being onthe opposite side of the side where the second light diffusion controlfilm is laminated.

The reason for this is that when the laminate is configured as such,incident light coming from a wide angle can be diffused more uniformly.

Furthermore, it is preferable that the thickness of the light diffusioncontrol plate is adjusted to a value within the range of 186 to 3,600μm.

The reason for this is that if the thickness of the light diffusioncontrol plate has a value of below 186 μm, the film thickness of thelight diffusion control films used becomes excessively thin, and whenthe light diffusion control plate is used as a projection screen,uniformly diffused light may not be obtained. On the other hand, it isbecause if the thickness of the light diffusion control plate has avalue of above 3,600 μm, the image may be blurred without being infocus, or the luminance may be decreased.

Therefore, it is more preferable that the lower limit of the thicknessof the light diffusion control plate is adjusted to a value of 255 μm orgreater, and even more preferably to a value of 315 μm or greater.

Also, it is more preferable that the upper limit of the thickness of thelight diffusion control plate is adjusted to a value of 2,000 μm orless, and even more preferably to a value of 1,200 μm or less.

3. Other Laminates

When a projection screen is configured, from the viewpoint of supportingthe light diffusion control plate and enhancing handleability, it ispreferable that a base material film is laminated on the incident sideof the light diffusion control plate.

Regarding such a base material film, it is preferable to use, forexample, a film of a polycarbonate, a polyallylate, polyether sulfone,an amorphous polyolefin, polyethylene terephthalate, or polymethylmethacrylate.

It is preferable that the thickness of the base material film isadjusted to a value within the range of, usually, 0.5 to 10 mm, and morepreferably to a value within the range of 2 to 8 mm.

Furthermore, lamination of the base material film on the light diffusioncontrol plate may be carried out by any lamination method such aslamination by means of a pressure-sensitive adhesive, lamination bymeans of an adhesive, or lamination based on autohesion propertieswithout using any adhesive; however, lamination by means of apressure-sensitive adhesive is particularly preferable.

In addition to that, from the viewpoint of preventing reflection ofexternal light to the viewer's side, an antireflection film may belaminated on the viewer's side of the light diffusion control film, or apressure-sensitive adhesive layer for fixing the projection screen to anadherend such as a window may also be laminated.

In the case of configuring the projection screen of the invention as arear projection screen, it is acceptable if the projection screencomprises at least a light diffusion control plate, and if necessary,the base material film, antireflection film, or pressure-sensitiveadhesive layer described above, or the like may be laminated thereon asappropriate.

Meanwhile, in the case of configuring the projection screen of theinvention as a front projection screen, it is acceptable if theprojection screen comprises at least a light diffusion control plate anda reflector plate, and if necessary, the base material film,antireflection film, or pressure-sensitive adhesive layer describedabove, or the like may be laminated thereon as appropriate.

EXAMPLES

Hereinafter, the invention will be described in more detail by way ofExamples.

Example 1

1. Synthesis of Component (B): Low-Refractive Index PolymerizableCompound

2 mol of isophorone diisocyanate (IPDI) and 2 mol of 2-hydroxyethylmethacrylate (HEMA) with respect to 1 mol of polypropylene glycol (PPG)having a weight average molecular weight of 9,200 were introduced into avessel, and then the mixture was allowed to react according to a routinemethod. Thus, a polyether urethane methacrylate having a weight averagemolecular weight of 9,900 was obtained.

The weight average molecular weights of polypropylene glycol andpolyether urethane methacrylate are values measured by gel permeationchromatography (GPC) under the following conditions and calculatedrelative to polystyrene standards.

-   -   GPC analyzer: manufactured by Tosoh Corp., HLC-8020    -   GPC column: manufactured by Tosoh Corp. (described below in the        order of passage)        -   TSK guard column HXL-H        -   TSK gel GMHXL (×2)        -   TSK gel G2000HXL    -   Measurement solvent: tetrahydrofuran    -   Measurement temperature: 40° C.

2. Preparation of Composition for Light Diffusion Control Film

Next, 150 parts by weight of o-phenylphenoxyethoxyethyl acrylaterepresented by Formula (3) described above and having a molecular weightof 268 (manufactured by Shin Nakamura Chemical Co., Ltd., NK ESTERA-LEN-10) as component (A), 20 parts by weight of2-hydroxy-2-methylpropiophenone (8 parts by weight with respect to thetotal amount (100 parts by weight) of component (A) and component (B))as component (C) were added to 100 parts by weight of polyether urethanemethacrylate having a weight average molecular weight of 9,900 ascomponent (B) thus obtained. Subsequently, the mixture was heated andmixed under the conditions of 80° C., and thus a composition for a lightdiffusion control film was obtained.

The refractive indices of component (A) and component (B) were measuredaccording to JIS K0062 using an Abbe refractometer (manufactured byAtago Co., Ltd., Abbe refractometer DR-M2, Na light source, wavelength589 nm), and the refractive indices were 1.58 and 1.46, respectively.

3. Coating Step

Next, the composition for a light diffusion control film thus obtainedwas applied on a transparent film-like polyethylene terephthalate as aprocess sheet that has been subjected to a release treatment, and thus acoating layer having a film thickness of 200 μm was formed.

4. First Irradiation with Ultraviolet Radiation

Next, as illustrated in FIG. 7B, the coating layer 1 was irradiated,using a linear light source, with light that was substantially parallellight when viewed from the axial direction of the linear light sourceand was non-parallel random light when viewed from another direction,such that the angle of irradiation θx illustrated in FIG. 8 was almost15°.

The peak illuminance at that time was 1.12 mW/cm², the cumulative amountof light was 22.8 mJ/cm², the lamp height was 500 mm, and the travelspeed of the coating layer was 0.2 m/min.

5. Second Irradiation with Ultraviolet Radiation

Next, after the step of performing first irradiation with ultravioletradiation, the exposed surface side of the coating layer was broughtinto a state in an oxygen-free atmosphere by laminating anultraviolet-transmitting release film having a thickness of 38 μm(manufactured by Lintec Corp., SP-PET382050) on the exposed surfaceside.

Next, as illustrated in FIG. 7C, the coating layer was irradiated withparallel light having a degree of parallelism of 2° or less using anultraviolet parallel light spot source (manufactured by Jatec Co.,Ltd.), for which the degree of parallelism of central light rays wascontrolled to be within ±3°, through the same side as that used in thestep for the first irradiation with ultraviolet radiation and throughthe release film, such that the angle of irradiation θx illustrated inFIG. 8 was almost 0°. Thus, a light diffusion control film having alouver-columnar structure and having a total film thickness of 200 μmwas obtained.

The peak illuminance at that time was 1.18 mW/cm², the cumulative amountof light was 24.1 mJ/cm², the lamp height was 240 mm, and the travelspeed of the coating layer was 0.2 m/min.

The peak illuminance and the cumulative amount of light were measured byinstalling a UV meter (manufactured by Eye Graphics Co., Ltd., EYEcumulative UV irradiation intensity tester UVPF-A1) equipped with aphotodetector at the position of the coating layer.

The film thickness of the light diffusion control film having alouver-columnar structure was measured using a constant pressurethickness measuring device (manufactured by Takara Co., Ltd., TECLOCKPG-02J).

A schematic diagram of a cross-section produced by cutting the lightdiffusion control film having a louver-columnar structure thus obtained,at a plane that was parallel to the direction of movement of the coatinglayer and was orthogonally intersecting the film plane, is presented inFIG. 12A, and a photograph of the cross-section is presented in FIG.12B.

As illustrated in FIG. 12A, the length L1 of the louver structure was113 μm, and the angle of inclination θ1 was 13°.

The length L2 of the columnar structure was 93 μm, and the angle ofinclination θ2 was 0°.

Furthermore, there was an overlapping internal structure formed as anedge of the pillar-shaped objects originating from the columnarstructure was in contact with the vicinity of an edge of theplate-shaped objects originating from the louver structure, and thelength L3 of the overlapping internal structure was 6 μm.

The value of θ1-θ2 in the overlapping internal structure was 13°.

Cutting of the light diffusion control film was performed using a razorblade, and capturing of photographs of the cross-section was performedby reflective observation using a digital microscope (manufactured byKeyence Corp., VHX-2000).

In the schematic diagram of FIG. 12A, the plate-shaped regions having arelatively high refractive index in the louver structure are indicatedwith solid lines, while the pillar-shaped objects in the columnarstructure are indicated with dotted lines (hereinafter, the same).

6. Light Diffusion Characteristics of Light Diffusion Control FilmHaving Louver-Columnar Structure

The light diffusion characteristics of the light diffusion control filmhaving a louver-columnar structure thus obtained were evaluated.

That is, a pressure-sensitive adhesive layer was provided on the releasefilm surface of the light diffusion control film having alouver-columnar structure, which was obtained in a state of beingsandwiched between a process sheet and a release film, and the lightdiffusion control film was adhered to a soda glass plate having athickness of 1.1 mm. This was used as a specimen for evaluation.

Next, as illustrated in FIG. 13A, light was caused to enter through theglass side of the specimen, that is, through the columnar structureside, at an angle of incidence θy of 0° with respect to the film plane,using a conoscope (manufactured by autronic-MELCHERS GmbH). A conoscopicimage thus obtained is presented in FIG. 13B.

7. Production of Light Diffusion Control Film Having Columnar StructureOnly

A light diffusion control film having a columnar structure only as theinternal structure as illustrated in FIGS. 14A and 14B was produced.

That is, the light diffusion control film having a columnar structureonly as illustrated in FIGS. 14A and 14B was produced in the same manneras in the case of the light diffusion control film having alouver-columnar structure illustrated in FIGS. 12A and 12B, except thatwhen the light diffusion control film was produced, the firstirradiation with ultraviolet radiation was not performed, the secondirradiation with ultraviolet radiation was performed in a state in whicha release film was not laminated, by changing the angle of irradiationto 0°, the peak illuminance to 1.24 mW/cm², and the cumulative amount oflight to 29.6 mJ/cm², and then the light diffusion control film wascompletely cured by irradiating the film with scattered light having arandom angle of irradiation in a state of having the release filmlaminated thereon.

Furthermore, the light diffusion characteristics of the resulting lightdiffusion control film having a columnar structure only representedsimple isotropic diffusion.

8. Production of Rear Projection Screen

Next, a plurality of sheets of the light diffusion control film thusobtained were laminated to obtain a light diffusion control plate, and abase material film was laminated on the light diffusion control platethus obtained. Thus, a rear projection screen was obtained.

That is, as illustrated in FIG. 15A, the light diffusion control filmhaving only a columnar structure as illustrated in FIGS. 14A and 14B(ID: none, PD: none), the light diffusion control film illustrated inFIGS. 12A and 12B (ID: ⇔, PD: →), the same light diffusion control film(ID: ⇔, PD: ←), and the same light diffusion control film (ID: ●, PD: ●)were in order from the side of a soda glass plate having a thickness of1.1 mm, and thus a laminate of soda glass plate/transparentpressure-sensitive adhesive layer/light diffusion control plate(laminate of light diffusion control film)/transparentpressure-sensitive adhesive layer/base material film (=soda glassplate/transparent pressure-sensitive adhesive layer/rear projectionscreen laminate) was obtained.

A polyethylene terephthalate film having a thickness of 100 μm was usedas the base material film.

The soda glass plate was considered as a constituent element of thelaminate under the assumption of an adherend of the rear projectionscreen.

9. Light Diffusion Characteristics of Rear Projection Screen

(1) Light Diffusion Characteristics in Case of Changing Incident Angle

For the specimen thus obtained, the light diffusion characteristics inthe case of varying the angle of incidence were evaluated.

That is, the laminate of soda glass plate/transparent pressure-sensitiveadhesive layer/rear projection screen thus obtained was directly used asa specimen for evaluation.

Next, as illustrated in FIG. 15A, light was caused to enter the specimenthrough the lower side of the specimen, that is, through the basematerial film side, while varying the incident angle θy in thetransverse direction on the paper plane to −30°, −20°, −10°, 0°, 10°,20°, and 30°, using a conoscope (manufactured by autronic-MELCHERSGmbH).

Similarly, light was caused to enter the specimen while varying theangle of incidence θ′y in a direction perpendicular to the paper planeto −30°, −20°, −10°, 0°, 10°, 20°, and 30°.

As illustrated in FIG. 15A, a conoscopic image in the case of viewingthe specimen from above is presented in FIG. 15B, and the luminanceobtained by measuring the diffused light corresponding to variousincident angles from the front direction of the screen, that is, theluminance (cd/m²) at the point of origin in the coordinate systems ofvarious conoscopic images, are presented in Table 1.

The luminance was measured using a conoscope.

(2) Transmission Gain

For the specimens thus obtained, perpendicular light was caused to enterthe specimens through the base material side at an incident angleθy=θ′y=0° with respect to the screen plane, and the transmission gainwas measured.

That is, first, perpendicular light at an incident angle θy=θ′y=0° wasmade incident to the specimen from a light source, and the frontluminance was measured using a conoscope. Thus, the front luminance(cd/m²) of the specimen was obtained.

Next, the illuminance of the light source was measured using anilluminometer (manufactured by Hioki E.E. Corporation, LUX HITESTER3423), and then the illuminance thus obtained was divided by π. Thus,the front luminance (cd/m²) of completely diffused light was calculated.

Next, the front luminance (cd/m²) was divided by the front luminance(cd/m²) of completely diffused light, and thus the transmission gain (−)was calculated. The results thus obtained are presented in Table 1.

(3) Brightness of Diffused Light

For the specimens thus obtained, the brightness of the diffused lightobtained in a case in which perpendicular light at an incident angle ofθy=θ′y=0° with respect to the screen plane was made incident to thespecimens through the base material side, was checked by visualinspection in front of the emission side of the screen.

Then, the brightness was compared with the brightness of diffused lightobtainable when light was caused to enter a commercially available rearprojection screen under similar conditions and was evaluated accordingto the following criteria. The results thus obtained are presented inTable 1.

At this time, SAIVIS MRPS-W100 manufactured by Mitsubishi Paper Mills,Ltd., which is a rear projection screen of a type capable of diffusinglight by means of microparticles included therein, was used.

⊙: Very bright compared to the commercially available rear projectionscreen

◯: Slightly bright compared to the commercially available rearprojection screen

Δ: Equally bright compared to the commercially available rear projectionscreen

X: Dim compared to the commercially available rear projection

(4) Image Evaluation Using Projector

For the specimens thus obtained, light for displaying particular imageswas caused to enter the specimens at different angles using a projector,and the quality of images was evaluated by visual inspection.

That is, as illustrated in FIG. 16, a specimen was disposed in front ofthe projector at a distance of 1 m from the projector.

At this time, the specimen was disposed in a direction in which lightcoming from the projector would be incident through the base materialfilm side.

Next, light from the projector was made incident at an incident angleθy=θ′y=0° with respect to the screen plane, an image projected on thespecimen was checked by visual inspection in front on the exit side ofthe specimen, and the images were evaluated according to the followingcriteria. The results thus obtained are presented in Table 1, and also,a photograph obtained at this time is presented in FIG. 17A.

The position of the specimen was shifted sideways to be parallel withthe screen plane, and incident light coming from the projector was madeincident at an incident angle of θy=−20° and θ′y=0° with respect to thescreen plane. An image projected on the specimen was checked by visualinspection in front on the exit side of the specimen, and the image wasevaluated according to the following criteria. The results thus obtainedare presented in Table 1, and also, a photograph obtained at this timeis presented in FIG. 17B.

Furthermore, the position of the specimen was shifted sideways to beparallel with the screen plane, and incident light from the projectorwas made incident at an incident angle of θy=−30° and θy=0° with respectto the screen plane. The image projected on the specimen was checked byvisual inspection, and the image was evaluated according to thefollowing criteria. The results thus obtained are presented in Table 1,and also, a photograph obtained at this time is presented in FIG. 17C.

In FIGS. 17A to 17C, it is understood that in all cases of θy=0°, −20°,and −30°, the unevenness of the light and shade in the images projectedon the specimen surface was very low, and the images were sufficientlybright for practical use.

⊙: In all of the images projected on the specimen at θy=0°, −20°, and−30°, the in-plane luminance checked by visual inspection is uniform,and the images are sufficiently bright for practical use.

◯: In two of the images projected on the specimen at θy=0°, −20°, and−30°, the in-plane luminance checked by visual inspection is uniform,and the images are sufficiently bright for practical use.

Δ: In one of the images projected on the specimen at θy=0°, −20°, and−30°, the in-plane luminance checked by visual inspection is uniform,and the images are sufficiently bright for practical use.

X: In all of the images projected on the specimen at θy=0°, −20°, and−30°, the in-plane luminance checked by visual inspection isnon-uniform, while the images are sufficiently bright for practical use.

Example 2

In Example 2, a rear projection screen was produced in the same manneras in Example 1, except that a laminate formed by laminating the lightdiffusion control film having a bent louver-columnar structure asillustrated in FIG. 19 (ID: ⇔, PD: →), the same light diffusion controlfilm (ID: ⇔, PD: ←), and the light diffusion control film illustrated inFIGS. 12A and 12B (ID: ●, PD: ●) in order from the side of the sodaglass plate, as illustrated in FIG. 18A, was used as the light diffusioncontrol plate, and the resulting rear projection screen was evaluated.The results thus obtained are presented in FIG. 18B and Table 1.

Meanwhile, the light diffusion control film having a bentlouver-columnar structure as illustrated in FIG. 19 was produced in thesame manner as in the case of the light diffusion control film having alouver-columnar structure of Example 1 as illustrated in FIGS. 12A and12B, except that 0.5 parts by weight of a benzotriazole-basedultraviolet absorber (manufactured by BASF SE, TINUVIN 384-2) ascomponent (D) (0.2 parts by weight with respect to the total amount (100parts by weight) of component (A) and component (B)) was further addedwhen the composition for a light diffusion control film was prepared.

Example 3

In Example 3, a rear projection screen was produced in the same manneras in Example 1, except that a laminate formed by laminating the lightdiffusion control film having a bent louver-columnar structure asillustrated in FIG. 19 (ID: ⇔, PD: →), the same light diffusion controlfilm (ID: ⇔, PD: ←), and the same light diffusion control film (ID: ●,PD: ●) in order from the side of the soda glass plate, as illustrated inFIG. 20A, was used as the light diffusion control plate, and theresulting rear projection screen was evaluated. The results thusobtained are presented in FIG. 20B and Table 1.

Example 4

In Example 4, a rear projection screen was produced in the same manneras in Example 1, except that a laminate formed by laminating the lightdiffusion control film having only a columnar structure as illustratedin FIGS. 14A and 14B (ID: none, PD: none), the light diffusion controlfilm having a bent louver-columnar structure as illustrated in FIG. 19(ID: ⇔, PD: →), the same light diffusion control film (ID: ⇔, PD: ←),and the same light diffusion control film (ID: ●, PD: ●) in order fromthe side of the soda glass plate, as illustrated in FIG. 21A, was usedas the light diffusion control plate, and the resulting rear projectionscreen was evaluated. The results thus obtained are presented in FIG.21B and Table 1.

Example 5

In Example 5, a rear projection screen was produced in the same manneras in Example 1, except that a laminate formed by laminating the lightdiffusion control film having a louver-columnar structure as illustratedin FIGS. 12A and 12B (ID: ●, PD: ●), the same light diffusion controlfilm (ID: ⇔, PD: →), and the same light diffusion control film (ID: ⇔,PD: ←) in order from the side of the soda glass plate, as illustrated inFIG. 22A, was used as the light diffusion control plate, and theresulting rear projection screen was evaluated. The results thusobtained are presented in FIG. 22B and Table 1.

Example 6

In Example 6, a rear projection screen was produced in the same manneras in Example 1, except that a laminate formed by laminating the lightdiffusion control film having a louver-columnar structure as illustratedin FIGS. 12A and 12B (ID: ●, PD: ●), the same light diffusion controlfilm (ID: ⇔, PD: ←), and the same light diffusion control film (ID: ⇔,PD: →) in order from the side of the soda glass plate, as illustrated inFIG. 23A, was used as the light diffusion control plate, and theresulting rear projection screen was evaluated. The results thusobtained are presented in FIG. 23B and Table 1.

Example 7

In Example 7, a rear projection screen was produced in the same manneras in Example 1, except that a laminate formed by laminating the lightdiffusion control film having only a columnar structure as illustratedin FIGS. 14A and 14B (ID: none, PD: none), the light diffusion controlfilm having only a columnar structure as illustrated in FIGS. 25A and25B (ID: none, PD: →), the same light diffusion control film (ID: ⇔, PD:←), and the light diffusion control film having only a columnarstructure as illustrated in FIGS. 14A and 14B (ID: none, PD: none) inorder from the side of the soda glass plate, as illustrated in FIG. 24A,was used as the light diffusion control plate, and the resulting rearprojection screen was evaluated. The results thus obtained are presentedin FIG. 24B and Table 1.

Meanwhile, the light diffusion control film having only a columnarstructure as illustrated in FIGS. 25A and 25B was produced in the samemanner as in the case of the light diffusion control film having alouver-columnar structure of Example 1 as illustrated in FIGS. 12A and12B, except that when the light diffusion control film was produced, thefirst irradiation with ultraviolet radiation was not performed, thesecond irradiation with ultraviolet radiation was performed in a statein which a release film was not laminated, by changing the angle ofirradiation to 0°, the peak illuminance to 1.19 mW/cm², and thecumulative amount of light to 27.5 mJ/cm², and then the light diffusioncontrol film was completely cured by irradiating the film with scatteredlight having a random angle of irradiation in a state of having therelease film laminated thereon.

Example 8

In Example 8, a rear projection screen was produced in the same manneras in Example 1, except that a laminate formed by laminating the lightdiffusion control film having only a columnar structure as illustratedin FIGS. 14A and 14B (ID: none, PD: none), the light diffusion controlfilm having a columnar-columnar structure as illustrated in FIGS. 27Aand 27B (ID: none, PD: →), the same light diffusion control film (ID:none, PD: ←), and the same light diffusion control film (ID: none, PD:●) in order from the side of the soda glass plate, as illustrated inFIG. 26A, was used as the light diffusion control plate, and theresulting rear projection screen was evaluated. The results thusobtained are presented in FIG. 26B, FIGS. 28A to 28C, and Table 2.

Furthermore, in FIGS. 28A to 28C, it is understood that in all cases ofθy=0°, −20°, and −30°, the unevenness of the light and shade in theimage projected on the specimen surface is very low, and the image issufficiently bright for practical use.

Meanwhile, the light diffusion control film having a columnar-columnarstructure as illustrated in FIGS. 27A and 27B was produced in the samemanner as in the case of the light diffusion control film having alouver-columnar structure of Example 1 as illustrated in FIGS. 12A and12B, except that when the light diffusion control film was produced, thefirst irradiation with ultraviolet radiation was performed with parallellight having a degree of parallelism of 2° or less, under the conditionsof an angle of irradiation of 20°, a peak illuminance of 1.05 mW/cm²,and a cumulative amount of light of 21.4 mJ/cm².

Example 9

In Example 9, a rear projection screen was produced in the same manneras in Example 1, except that a laminate formed by laminating the lightdiffusion control film having only a columnar structure as illustratedin FIGS. 14A and 14B (ID: none, PD: none), the light diffusion controlfilm having a bent columnar-columnar structure as illustrated in FIGS.30A and 30B (ID: none, PD: →), the same light diffusion control film(ID: none, PD: ←), and the same light diffusion control film (ID: none,PD: ●) in order from the side of the soda glass plate, as illustrated inFIG. 29A, was used as the light diffusion control plate, and theresulting rear projection screen was evaluated. The results thusobtained are presented in FIG. 29B and Table 2.

Meanwhile, the light diffusion control film having a bentcolumnar-columnar structure as illustrated in FIGS. 30A and 30B wasproduced by further adding, when the composition for a light diffusioncontrol film was prepared, 0.5 parts by weight of a benzotriazole-basedultraviolet absorber (manufactured by BASF SE, TINUVIN 384-2) ascomponent (D) (0.2 parts by weight with respect to the total amount (100parts by weight) of component (A) and component (B)) to the composition.

Furthermore, the light diffusion control film was produced in the samemanner as in the case of the light diffusion control film having alouver-columnar structure of Example 1 as illustrated in FIGS. 12A and12B, except that when the light diffusion control film was produced, thefirst irradiation with ultraviolet radiation was performed with parallellight having a degree of parallelism of 2° or less, under the conditionsof an angle of irradiation of 20°, a peak illuminance of 1.05 mW/cm, anda cumulative amount of light of 21.4 mJ/cm².

Example 10

In Example 10, a rear projection screen was produced in the same manneras in Example 1, except that a laminate formed by laminating the lightdiffusion control film having only a columnar structure as illustratedin FIGS. 14A and 14B (ID: none, PD: none), the light diffusion controlfilm having a louver-columnar structure as illustrated in FIGS. 12A and12B (ID: ●, PD: ●), the same light diffusion control film (ID: ⇔, PD:→), and the same light diffusion control film (ID: ⇔, PD: ←) in orderfrom the side of the soda glass plate, as illustrated in FIG. 31A, wasused as the light diffusion control plate, and the resulting rearprojection screen was evaluated. The results thus obtained are presentedin FIG. 31B and Table 2.

Example 11

In Example 11, a rear projection screen was produced in the same manneras in Example 1, except that a laminate formed by laminating the lightdiffusion control film having a columnar-columnar structure asillustrated in FIGS. 27A and 27B (ID: none, PD: →), the same lightdiffusion control film (ID: none, PD: ←), and the same light diffusioncontrol film (ID: none, PD: ●) in order from the side of the soda glassplate, as illustrated in FIG. 32A, was used as the light diffusioncontrol plate, and the resulting rear projection screen was evaluated.The results thus obtained are presented in FIG. 32B and Table 2.

Example 12

In Example 12, a rear projection screen was produced in the same manneras in Example 1, except that a laminate formed by laminating the lightdiffusion control film having a bent columnar-columnar structure asillustrated in FIGS. 30A and 30B (ID: none, PD: →), the same lightdiffusion control film (ID: none, PD: ←), and the same light diffusioncontrol film (ID: none, PD: ●) in order from the side of the soda glassplate, as illustrated in FIG. 33A, was used as the light diffusioncontrol plate, and the resulting rear projection screen was evaluated.The results thus obtained are presented in FIG. 33B and Table 2.

Example 13

In Example 13, a rear projection screen was produced in the same manneras in Example 1, except that a laminate formed by laminating the lightdiffusion control film having only a columnar structure as illustratedin FIGS. 14A and 14B (ID: none, PD: none), the light diffusion controlfilm having a louver-columnar structure as illustrated in FIGS. 12A and12B (ID: ⇔, PD: ←), the same light diffusion control film (ID: ⇔, PD:→), and the same light diffusion control film (ID: ●, PD: ●) in orderfrom the side of the soda glass plate, as illustrated in FIG. 34A, wasused as the light diffusion control plate, and the resulting rearprojection screen was evaluated. The results thus obtained are presentedin FIG. 34B and Table 2.

Comparative Example 1

In Comparative Example 1, a rear projection screen was produced in thesame manner as in Example 1, except that a laminate formed by laminatingthe light diffusion control film having a columnar-columnar structure asillustrated in FIGS. 12A and 12B (ID: ⇔, PD: →), the same lightdiffusion control film (ID: ⇔, PD: ←), and the same light diffusioncontrol film (ID: ●, PD: ●) in order from the side of the soda glassplate, as illustrated in FIG. 35A, was used as the light diffusioncontrol plate, and the resulting rear projection screen was evaluated.The results thus obtained are presented in FIG. 35B and Table 3.

Comparative Example 2

In Comparative Example 2, a rear projection screen was produced in thesame manner as in Example 1, except that the light diffusion controlfilm having only a columnar structure as illustrated in FIGS. 14A and14B (ID: none, PD: none) was used as the light diffusion control plateas illustrated in FIG. 36A, and the resulting rear projection screen wasevaluated. The results thus obtained are presented in FIG. 36B, FIGS.37A to 37C, and Table 3.

Furthermore, in FIGS. 37A to 37C, it is understood that the marginalportions are dimmed because the range of the light diffusioncharacteristics of the light diffusion control film having a columnarstructure only is narrow particularly when θy=0° or −20°.

Comparative Example 3

In Comparative Example 3, a rear projection screen was produced in thesame manner as in Example 1, except that a laminate formed by laminatingthe light diffusion control film having only a louver structure asillustrated in FIGS. 39A and 39B (ID: ⇔, PD: none) and the same lightdiffusion control film (ID: ●, PD: none) in order from the side of thesoda glass plate, as illustrated in FIG. 38A, was used as the lightdiffusion control plate, and the resulting rear projection screen wasevaluated. The results thus obtained are presented in FIG. 38B, FIGS.40A to 40C, and Table 3.

In FIGS. 40A to 40C, it is understood that even at θy=0°, uniformity ofthe diffused light is low, and unevenness of the light and shade occurs.Furthermore, it is understood that when θy=−20° and −30°, any one sidein the transverse direction is dimmed because the range of the lightdiffusion characteristics is narrow.

Meanwhile, the light diffusion control film having only a louverstructure as illustrated in FIGS. 39A and 39B was produced in the samemanner as in the case of the light diffusion control film having alouver-columnar structure of Example 1 as illustrated in FIGS. 12A and12B, except that when the light diffusion control film was produced, thefilm thickness of the coating layer was adjusted to 165 μm; the firstirradiation with ultraviolet radiation was performed under theconditions of an angle of irradiation of 0°, a peak illuminance of 2.55mW/cm², and a cumulative amount of light of 39.2 mJ/cm²; the secondirradiation with ultraviolet radiation was not performed; and instead,the light diffusion control film was completely cured by irradiating thefilm with scattered light having a random angle of irradiation in astate of having a release film laminated thereon.

Comparative Example 4

In Comparative Example 4, a rear projection screen was produced in thesame manner as in Example 1, except that a laminate formed by laminatingthe light diffusion control film having only a louver structure asillustrated in FIGS. 42A and 42B (ID: ⇔, PD: ←), the same lightdiffusion control film (ID: ⇔, PD: →), a light diffusion control filmhaving only a louver structure as illustrated in FIGS. 39A and 39B (ID:⇔, PD: none), and the same light diffusion control film (ID: ●, PD:none) in order from the side of the soda glass plate, as illustrated inFIG. 41A, was used as the light diffusion control plate, and theresulting rear projection screen was evaluated. The results thusobtained are presented in FIG. 41B, FIGS. 43A to 43C, and Table 3.

In FIGS. 43A to 43C, it is understood that although the range of thelight diffusion characteristics has been expanded, in all cases ofθy=0°, −20°, and −30°, the uniformity of the diffused light is low, andthe unevenness of the light and shade occurs.

Meanwhile, the light diffusion control film having only a louverstructure as illustrated in FIGS. 42A and 42B was produced in the samemanner as in the case of the light diffusion control film having alouver-columnar structure of Example 1 as illustrated in FIGS. 12A and12B, except that when the light diffusion control film was produced, thefilm thickness of the coating layer was adjusted to 165 μm; the firstirradiation with ultraviolet radiation was performed under theconditions of an angle of irradiation of 15°, a peak illuminance of 2.42mW/cm², and a cumulative amount of light of 37.0 mJ/cm²; the secondirradiation with ultraviolet radiation was not performed; and instead,the light diffusion control film was completely cured by irradiating thefilm with scattered light having a random angle of irradiation in astate of having a release film laminated thereon.

TABLE 1 Luminance (cd/m²) L3 (−30°) L3 (−20°) L3 (−10°) L0 (0°) L2 (10°)L2 (20°) Proportion or luminance relative to L0 (—) L1 L1 L1 L2 L1 L1 L1L1/L0 L1/L0 L1/L0 (30°) (20°) (10°) (30°) (−10°) (−20°) (−30°) (30°)(20°) (10°) Example 8.39 1 24.91 35.30 14.59 19.34 33.92 41.34 35.8923.15 16.85 0.35 0.47 0.82 35.36 25.90 24.86 Example 6.18 2 19.88 36.4312.41 15.18 33.33 45.78 36.21 17.32 12.64 0.27 0.33 0.73 36.36 22.6823.86 Example 5.97 3 17.45 30.51 10.92 13.58 28.25 38.81 30.88 15.5711.43 0.28 0.35 0.73 30.35 18.48 19.58 Example 6.62 4 15.45 20.65 9.4512.12 20.23 24.36 21.32 14.28 10.64 0.39 0.50 0.83 20.72 14.78 14.46Example 5.94 5 20.03 49.68 30.84 30.85 44.83 64.17 48.13 34.27 37.090.48 0.48 0.70 52.88 27.57 16.68 Example 3.95 6 15.33 41.98 21.99 32.0335.23 54.54 59.74 33.30 24.53 0.40 0.59 0.65 49.55 30.26 18.08 Example15.55 7 20.08 22.74 17.90 19.92 22.51 24.14 22.93 18.04 14.85 0.74 0.830.93 23.26 20.46 15.32 Proportion or luminance relative to L0 (—) L3/L0(−30°) L3/L0 (−20°) L3/L0 (−10°) L0/L0 (0°) L2/L0 (10°) L2/L0 BrightnessImage (20°) Transmission of evaluation L2/L0 L1/L0 L1/L0 L1/L0 gaindiffused using (30°) (−10°) (−20°) (−30°) (—) light projector Example0.20 2.00 ⊙ ⊙ 1 0.60 0.85 1.00 0.87 0.56 0.41 0.86 0.63 0.60 Example0.13 2.21 ⊙ ◯ 2 0.43 0.80 1.00 0.79 0.38 0.28 0.79 0.50 0.52 Example0.15 1.87 ◯ ◯ 3 0.45 0.79 1.00 0.80 0.40 0.29 0.78 0.48 0.50 Example0.27 1.18 Δ ⊙ 4 0.63 0.85 1.00 0.88 0.59 0.44 0.85 0.61 0.59 Example0.09 3.10 ⊙ ◯ 5 0.31 0.77 1.00 0.75 0.53 0.58 0.82 0.43 0.26 Example0.07 2.63 ⊙ ◯ 6 0.28 0.77 1.00 1.10 0.61 0.45 0.91 0.55 0.33 Example0.64 1.17 Δ ⊙ 7 0.83 0.94 1.00 0.95 0.75 0.62 0.96 0.85 0.63

TABLE 2 Luminance (cd/m²) L3 (−30°) L3 (−20°) L3 (−10°) L0 (0°) L2 (10°)L2 (20°) Proportion of luminance relative to L0 (—) L1 L1 L1 L2 L1 L1 L1L1/L0 L1/L0 L1/L0 (30°) (20°) (10°) (30°) (−10°) (−20°) (−30°) (30°)(20°) (10°) Example 14.61 8 22.22 23.34 13.65 19.45 22.93 23.95 22.9018.54 12.71 0.58 0.81 0.96 23.19 18.93 16.90 Example 13.70 9 17.52 19.0913.79 17.07 19.37 20.23 19.39 17.42 14.25 0.68 0.84 0.96 19.28 16.5714.76 Example 7.97 10 21.33 36.57 24.89 26.09 35.67 42.63 36.78 29.6227.91 0.58 0.61 0.84 38.45 27.32 19.57 Example 16.77 11 27.82 31.9717.75 25.27 32.10 35.11 33.72 26.70 17.83 0.51 0.72 0.91 32.60 25.2922.74 Example 15.14 12 20.96 23.13 15.89 20.43 23.72 24.95 23.75 20.4815.51 0.64 0.82 0.95 23.45 19.37 16.83 Example 7.61 13 26.66 43.95 19.9331.77 40.05 41.86 34.34 22.29 15.70 0.48 0.76 0.96 27.43 26.88 22.41Proportion of luminance relative to L0 (—) L3/L0 (−30°) L3/L0 (−2 0°)L3/L0 (−10°) L0/L0 (0°) L2/ L0 (10°) L2/L0 Brightness Image (20°)Transmission of evaluation L2/L0 L1/L0 L1/L0 L1/L0 gain diffused using(30°) (−10°) (−20°) (−30°) (—) light projector Example 0.61 1.16 Δ ⊙ 80.93 0.97 1.00 0.96 0.77 0.53 0.97 0.79 0.71 Example 0.68 0.98 Δ ⊙ 90.87 0.94 1.00 0.96 0.86 0.70 0.95 0.82 0.73 Example 0.19 2.06 ⊙ ⊙ 100.50 0.86 1.00 0.86 0.69 0.65 0.90 0.64 0.46 Example 0.48 1.70 ◯ ⊙ 110.79 0.91 1.00 0.96 0.76 0.51 0.93 0.72 0.65 Example 0.61 1.21 Δ ⊙ 120.84 0.93 1.00 0.95 0.82 0.62 0.94 0.78 0.67 Example 0.18 2.02 ⊙ ⊙ 130.64 1.05 1.00 0.82 0.53 0.38 0.66 0.64 0.54

TABLE 3 Luminance (cd/m²) L3 (−30°) L3 (−20°) L3 (−10°) L0 (0°) L2 (10°)L2 (20°) Proportion of luminance relative to L0 (—) L1 L1 L1 L2 L1 L1 L1L1/L0 L1/L0 L1/L0 (30°) (20°) (10°) (30°) (−10°) (−20°) (−30°) (30°)(20°) (10°) Comparative 4.27 Example 1 16.21 50.38 16.86 20.88 49.8969.43 52.37 24.07 19.07 0.24 0.30 0.72 48.09 31.25 31.53 Comparative3.15 Example 2 22.24 124.26 2.94 21.65 143.71 265.18 149.39 22.24 2.520.01 0.08 0.54 179.76 39.82 4.60 Comparative 5.60 Example 3 37.28 131.532.79 15.96 107.63 185.29 104.18 14.35 2.44 0.02 0.09 0.58 120.14 28.464.60 Comparative 4.30 Example 4 15.49 43.10 11.38 42.53 54.14 56.6456.20 51.70 13.67 0.20 0.75 0.96 41.01 13.31 4.09 Proportion ofluminance relative to L0 (—) L3/L0 (−30°) L3/L0 (−20°) L3/L0 (−10°)L0/L0 (0°) L2/L0 (10°) L2/L0 Brightness Image (20°) Transmission ofevaluation L2/L0 L1/L0 L1/L0 L1/L0 gain diffused using (30°) (−10°)(−20°) (−30°) (—) light projector Comparative 0.06 3.35 ⊙ Δ Example 10.23 0.73 1.00 0.76 0.35 0.27 0.69 0.45 0.45 Comparative 0.01 12.81 ⊙ ΔExample 2 0.08 0.47 1.00 0.56 0.08 0.01 0.68 0.15 0.02 Comparative 0.038.95 ⊙ X Example 3 0.20 0.71 1.00 0.56 0.08 0.01 0.65 0.15 0.02Comparative 0.08 2.74 ⊙ X Example 4 0.27 0.76 1.00 0.99 0.91 0.24 0.720.23 0.07

As discussed above, according to the invention, when a light diffusioncontrol plate including a light diffusion control film having apredetermined internal structure in the interior of the film is used,and when the light diffusion characteristics obtainable in the case ofvarying the incident angle of incident light in two particulardirections that orthogonally intersect each other along the surface ofsuch a light diffusion control plate are defined to be in apredetermined range, a projection screen which can effectively diffuseincident light coming from a wide range of angles in the transversedirection and the vertical direction, and has a wide viewing angle evenin a case in which the projection screen is applied to a large-sizedscreen, can be obtained.

Therefore, it is expected that the projection screen of the inventionremarkably contributes to quality enhancement of projection screens.

REFERENCE SIGNS

1: coating layer, 1′: internal structure-unformed region, 2: processsheet, 10, 10′, 10″, 10′″: light diffusion control film, 11:plate-shaped region having relatively low refractive index, 12:plate-shaped region having relatively high refractive index, 14:pillar-shaped object having relatively high refractive index, 16: bentportion, 20: first internal structure, 20 s: columnar structure, 20 s′:bent columnar structure, 20 t′: bent louver structure, 20 u:predetermined internal structure obtainable by arranging flaky objectshaving relatively high refractive index in region having relatively lowrefractive index, 20 u′: predetermined bent internal structure havingbent portion, 30: second internal structure, 30 s: columnar structure,40: overlapping internal structure, 50: light diffusion layer, 60:parallel light, 70′: light that is substantially parallel light whenviewed from one direction and is non-parallel random light when viewedfrom another direction, 125: linear light source

DRAWINGS

FIG. 1

LIGHT DIFFUSION INCIDENT ANGLE DOMAIN

FIG. 3

INCIDENT LIGHT

FIG. 4

INCIDENT LIGHT

FIG. 11A

LUMINANCE L₁

FIG. 11B

LUMINANCE L₂

FIG. 12A

COLUMNAR STRUCTURE

LOUVER STRUCTURE

FIG. 13A

GLASS SIDE

FIG. 14A

COLUMNAR STRUCTURE

FIG. 15A

OBSERVER

SODA GLASS PLATE

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

BASE MATERIAL FILM

LIGHT DIFFUSION CONTROL FILM (ID: NONE, PD: NONE)

LIGHT DIFFUSION CONTROL FILM

LIGHT DIFFUSION CONTROL FILM

LIGHT DIFFUSION CONTROL FILM

REAR PROJECTION SCREEN

LIGHT DIFFUSION CONTROL PLATE

FIG. 16

PROJECTOR

INCIDENT LIGHT

OBSERVER

SPECIMEN

FIG. 17

EXAMPLE 1

FIG. 18A

OBSERVER

SODA GLASS PLATE

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

BASE MATERIAL FILM

LIGHT DIFFUSION CONTROL FILM

LIGHT DIFFUSION CONTROL FILM

LIGHT DIFFUSION CONTROL FILM

FIG. 19

COLUMNAR STRUCTURE

BENT LOUVER STRUCTURE

FIG. 20A

OBSERVER

SODA GLASS PLATE

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

BASE MATERIAL FILM

LIGHT DIFFUSION CONTROL FILM

LIGHT DIFFUSION CONTROL FILM

LIGHT DIFFUSION CONTROL FILM

FIG. 21A

OBSERVER

SODA GLASS PLATE

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

BASE MATERIAL FILM

LIGHT DIFFUSION CONTROL FILM (ID: NONE, PD: NONE)

LIGHT DIFFUSION CONTROL FILM

LIGHT DIFFUSION CONTROL FILM

LIGHT DIFFUSION CONTROL FILM

FIG. 22A

OBSERVER

SODA GLASS PLATE

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

BASE MATERIAL FILM

LIGHT DIFFUSION CONTROL FILM

LIGHT DIFFUSION CONTROL FILM

LIGHT DIFFUSION CONTROL FILM

FIG. 23A

OBSERVER

SODA GLASS PLATE

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

BASE MATERIAL FILM

LIGHT DIFFUSION CONTROL FILM

LIGHT DIFFUSION CONTROL FILM

LIGHT DIFFUSION CONTROL FILM

FIG. 24A

OBSERVER

SODA GLASS PLATE

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

BASE MATERIAL FILM

LIGHT DIFFUSION CONTROL FILM (ID: NONE, PD: NONE)

LIGHT DIFFUSION CONTROL FILM (ID: NONE)

LIGHT DIFFUSION CONTROL FILM (ID: NONE)

LIGHT DIFFUSION CONTROL FILM (ID: NONE, PD: NONE)

FIG. 25A

COLUMNAR STRUCTURE

FIG. 26A

OBSERVER

SODA GLASS PLATE

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

BASE MATERIAL FILM

LIGHT DIFFUSION CONTROL FILM (ID: NONE, PD: NONE)

LIGHT DIFFUSION CONTROL FILM (ID: NONE)

LIGHT DIFFUSION CONTROL FILM (ID: NONE)

LIGHT DIFFUSION CONTROL FILM (ID: NONE)

FIG. 27A

COLUMNAR STRUCTURE

COLUMNAR STRUCTURE

FIG. 28

EXAMPLE 8

FIG. 29A

OBSERVER

SODA GLASS PLATE

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

BASE MATERIAL FILM

LIGHT DIFFUSION CONTROL FILM (ID: NONE, PD: NONE)

LIGHT DIFFUSION CONTROL FILM (ID: NONE)

LIGHT DIFFUSION CONTROL FILM (ID: NONE)

LIGHT DIFFUSION CONTROL FILM (ID: NONE)

FIG. 30A

COLUMNAR STRUCTURE

BENT COLUMNAR STRUCTURE

FIG. 31A

OBSERVER

SODA GLASS PLATE

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

BASE MATERIAL FILM

LIGHT DIFFUSION CONTROL FILM (ID: NONE, PD: NONE)

LIGHT DIFFUSION CONTROL FILM

LIGHT DIFFUSION CONTROL FILM

LIGHT DIFFUSION CONTROL FILM

FIG. 32A

OBSERVER

SODA GLASS PLATE

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

BASE MATERIAL FILM

LIGHT DIFFUSION CONTROL FILM (ID: NONE)

LIGHT DIFFUSION CONTROL FILM (ID: NONE)

LIGHT DIFFUSION CONTROL FILM (ID: NONE)

FIG. 33A

OBSERVER

SODA GLASS PLATE

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

BASE MATERIAL FILM

LIGHT DIFFUSION CONTROL FILM (ID: NONE)

LIGHT DIFFUSION CONTROL FILM (ID: NONE)

LIGHT DIFFUSION CONTROL FILM (ID: NONE)

FIG. 34A

OBSERVER

SODA GLASS PLATE

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

BASE MATERIAL FILM

LIGHT DIFFUSION CONTROL FILM (ID: NONE, PD: NONE)

LIGHT DIFFUSION CONTROL FILM

LIGHT DIFFUSION CONTROL FILM

LIGHT DIFFUSION CONTROL FILM

FIG. 35A

OBSERVER

SODA GLASS PLATE

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

BASE MATERIAL FILM

LIGHT DIFFUSION CONTROL FILM

LIGHT DIFFUSION CONTROL FILM

LIGHT DIFFUSION CONTROL FILM

FIG. 36A

OBSERVER

SODA GLASS PLATE

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

BASE MATERIAL FILM

LIGHT DIFFUSION CONTROL FILM (ID: NONE, PD: NONE)

FIG. 37

COMPARATIVE EXAMPLE 2

FIG. 38A

OBSERVER

SODA GLASS PLATE

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

BASE MATERIAL FILM

LIGHT DIFFUSION CONTROL FILM (PD: NONE)

LIGHT DIFFUSION CONTROL FILM (PD: NONE)

FIG. 39A

LOUVER STRUCTURE

FIG. 40

COMPARATIVE EXAMPLE 3

FIG. 41A

OBSERVER

SODA GLASS PLATE

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

TRANSPARENT PRESSURE-SENSITIVE ADHESIVE LAYER

BASE MATERIAL FILM

LIGHT DIFFUSION CONTROL FILM

LIGHT DIFFUSION CONTROL FILM

LIGHT DIFFUSION CONTROL FILM (PD: NONE)

LIGHT DIFFUSION CONTROL FILM (PD: NONE)

FIG. 42A

LOUVER STRUCTURE

FIG. 43

COMPARATIVE EXAMPLE 4

FIG. 45

DIRECTION OF LIGHT DIFFUSION ANGLE RANGE

DIRECTION OF LIGHT DIFFUSION ANGLE RANGE

What is claimed is:
 1. A projection screen comprising light diffusioncontrol plate, the light diffusion control plate including a lightdiffusion control film having an internal structure including aplurality of regions having a relatively high refractive index in aregion having a relatively low refractive index in the interior of thefilm, wherein when a first direction and a second direction orthogonallyintersecting each other are assumed to be on the surface of the lightdiffusion control plate, and when the incident angle of the lightincident to the light diffusion control plate is defined such that anangle parallel to the normal line to the surface of the light diffusioncontrol plate is defined as 0°, in a case in which the luminance ofdiffused light obtainable when light is incident on the intersectionpoint of the orthogonally intersecting first direction and seconddirection at an incident angle of 0° is designated as L₀ (cd/m²); theluminance of diffused light obtainable when light is incident on theintersection point of the orthogonally intersecting first direction andsecond direction at an incident angle varying in the range of −30° to30° along the first direction is designated as L₁ (cd/m²); and theluminance of diffused light obtainable when light is incident on theintersection point of the orthogonally intersecting first direction andsecond direction at an incident angle varying in the range of 0° to 30°along the second direction is designated as L₂ (cd/m²), there exist thefirst direction and the second direction, in which L₀, L₁, and L₂ alwayssatisfy the following relational expressions (1) and (2), wherein in acase in which the luminance of diffused light obtainable when light isincident on the intersection point of the orthogonally intersectingfirst direction and second direction at an incident angle of −30° alongthe second direction is designated as) L₃(−30°) (cd/m²), L₃(−30°)satisfies the following relational expression (3):L ₁≥0.25×L ₀  (1)L ₂≥0.25×L ₀  (2)L ₃(−30°)<0.7×L ₀  (3).
 2. The projection screen according to claim 1,wherein in the light diffusion control plate, the transmission gain atthe time of setting the incident angle to 0° is adjusted to a value of0.8 or higher.
 3. The projection screen according to claim 1, whereinthe light diffusion control plate is formed by laminating a plurality ofsheets of a light diffusion control film, and the number of laminatedsheets of the light diffusion control film is adjusted to 4 or less. 4.The projection screen according to claim 1, wherein the light diffusioncontrol film includes a light diffusion control film having a singlelight diffusion layer that has a first internal structure and a secondinternal structure, the structures each including a plurality of regionshaving a relatively high refractive index in a region having arelatively low refractive index in the interior of the film,sequentially from the lower part along the film thickness direction. 5.The projection screen according to claim 4, wherein the light diffusioncontrol film has an overlapping internal structure in which the upperend portion of the first internal structure and the position of thelower end portion of the second internal structure overlap each other inthe film thickness direction.
 6. The projection screen according toclaim 5, wherein the thickness of the overlapping internal structure isadjusted to a value within the range of 1 to 40 μm.
 7. The projectionscreen according to claim 4, wherein the incident angle θ1 of the regionhaving a relatively high refractive index in the first internalstructure with respect to the normal line to the film plane is adjustedto a value within the range of 0° to 80°, and the incident angle θ2 ofthe region having a relatively high refractive index in the secondinternal structure with respect to the normal line to the film plane isadjusted to a value within the range of 0° to 45°.
 8. The projectionscreen according to claim 4, wherein the first internal structure is acolumnar structure obtainable by arranging a plurality of pillar-shapedobjects having a relatively high refractive index to stand closetogether in the film thickness direction in a region having a relativelylow refractive index, or a louver structure obtainable by alternatelyarranging a plurality of plate-shaped regions having differentrefractive indices in any one direction along the film plane.
 9. Theprojection screen according to claim 4, wherein the second internalstructure is a columnar structure obtainable by arranging a plurality ofpillar-shaped objects having a relatively high refractive index to standclose together in the film thickness direction in a region having arelatively low refractive index, or a louver structure obtainable byalternately arranging a plurality of plate-shaped regions havingdifferent refractive indices in any one direction along the film plane.10. The projection screen according to claim 1, wherein the thickness ofthe light diffusion control plate is adjusted to a value within therange of 186 to 3,600 μm.